Regarding the steamrolled outpost problem, you could automatically rebuild/repair colonies until the player explicitly forfeits them. As long as the route doesn't cross disputed or enemy space, transport ships can bring people and materials to the damaged colony.
Whenever an outpost is indeed steamrolled, the player only need to send reinforcements to protect it (maybe by diverting enemy forces elsewhere, not necessarily with a localized patrol effort) and the colony will be eventually restored.
There would be a strong similarity with the initial creation of the colony; you choose a planet and a colony blueprint and the colony is built as fast as you provide resources (e.g. from mining colonies). You can also include planet defense fleets in colony blueprints; newly made ships join the defense forces of nearby understaffed planets requiring them or, if not needed, one of the mobile fleets the player defined.
The technique of blueprints of what you want in a colony, battle fleet etc. could be refined with evolutionary steps (mining colony example: first 1 habitat, offices and 1 anti-aircraft battery; then 2 habitats, 1 mine and 2 cruisers; then increments of 5 habitats, 1 mine, 1 factory, 1 anti-aircraft battery, 3 cruisers; then when mining sites run out increments of 3 habitats, 1 research facility, 1 factory, 1 anti-aircraft battery, 2 cruisers), ratios (mining colony example: 1 spaceport every 2 mines or 3 factories, 1 AA battery every 4 habitats, 1 research facility every 9 habitats 1 mine every 3 habitats, 1 factory every 2 mines until sites run out then 1 every 3 habitats, 1 cruiser every 2 habitats), alternate configurations (e.g. a "underpopulated" colony avoids labor-intensive stuff, a "war effort" colony builds more spaceships and less of everything else) and other helpful abstractions to save the player tedious adjustments.

Regarding the tower defense aspect, a self-healing empire that doesn't require micromanagement makes continuous enemy attacks sustainable and not annoying; mobile fleets can be used to conquer new worlds and to meet other large fleets. Consider an alternative to constant, preplanned attacks: major attacks triggered by empire prosperity thresholds: large swarm fleets when the player exceeds a certain number of spaceships, genocide attempts when the player exceeds a certain population, structured conquest forces when the player exceeds a certain number of worlds, special stuff after certain advanced technological improvements are obtained, and a huge do-or-die final attack when the player conquers the whole sector.

I still wonder if such a game should be:
1) war focused (mostly combat) [just like all 4X games]
2) non war focused (mostly court politics, internal issues, assigning officials) [I don't recall ever seeing a game like that]

Your thoughts?

Non war focused could be interesting. It would allow you to dig deeper in economics and politics without having to tie everything to starship production. I would set the goal to produce a resource intensive wonder as fast as possible. The gameplay is then centered on how to be as efficient as possible in managing the empire. If you throw in random events to throw the player off balance, it will be as interesting as nuking aliens.

non war focused would be really interesting. Since you can play at your own pace, and also a stock market would be cool.

Non war focused could be interesting. It would allow you to dig deeper in economics and politics without having to tie everything to starship production. I would set the goal to produce a resource intensive wonder as fast as possible. The gameplay is then centered on how to be as efficient as possible in managing the empire. If you throw in random events to throw the player off balance, it will be as interesting as nuking aliens.

Yes, might be interesting... But it does not sound thrilling, it does not make "want to play it", does not make me "wow, finally someone made it, I waited for it my whole life"

I think the non combat focused thing is desirable (some people like the concept), but when we come to details "the goal is to produce a resource intensive wonder as fast as possible" it is unthrilling... In contrast "lash a mayhem across the galaxy conquering other pathetic races" seems much more interesting and fun

Is it because war is inheritably more fun or because we miss something? Or maybe it is only my impression and you find "building a resource intensive wonder/project" more thrilling than conquest?

I was thinking, what would make me "wow" for a non combat focused gameplay and I found so far only one case. Intrigue. The assassins trying to take my life, usurpers trying to overthrow me from my beloved throne and court intrigues of my courtiers (which rarely benefit the empire or me). I mean, if I were to play as an emperor I still need a thrill of some sort. I like economy, like it a lot, I think most games focus too much on military/combat and I don't like it too much, still... If I were just to build an empire in a SimCity like style... I don't know, I feel something is missing there for me.

Your thoughts?

People, please try to say something and/or comment more on what is already posted. It's a brainstorming phase, so it does not have to be compatible with other things at the moment. Don't tell me you have nothing to say about space empires topic. Even a simple one word comment like "it's lame/ok/love it" about an idea would be a help to me.

Another concept (sectors):

The universe divided into 5x5 sectors (=25) with around 10 planets per sector. So it means all planets of a sector are displayed on one screen without any scrolling and zooming. At the first glance it looks like tons (250) planets to colonize, but the outer sectors would be progressively dangerous, so in practice most of the player's empire would be in the central 9 sectors. I did some drawings and it looks quite nice and convenient. The sectors would be not only for display purposes but also functional. The enemy AI would be very reluctant to go to other sectors unless their current one is not fully conquered yet. The movement to another sector would be more expensive than movement inside a sector. There would be several sector wide options (the player could make separate laws for sectors instead of individual planets) and dangers (each sector would have their own space pirate that plunder sector planets only, all plagues would be limited to a single sector). So, sectors would be partially separate ecosystems.

The player, as an emperor, would be limited in the number of actions he can do. Like he could make up to 3 attacks and 6 fleet movements per turn (empire wide). So, huge fleet stationing everywhere is OK and maybe even desirable for defense purposes, but for invasion one need to learn how to concentrate forces That would cut down on micromanagement greatly I guess, which is always nice. Another limited action would be assigning officials/agents to planets (like tax collectors, propaganda corps, field medical team in case of plague), the player could put like 5 of these per turn max (actually, it would use emperor's stamina system, so it would not be "let's see which 5 I should assign this turn") but the trick is these can not be moved again. Once placed these are placed and can not be moved anymore (which sometimes might be good, in case of tax collectors and sometimes bad in case of medics when the plague already ended), the player would have an "recall order" option (not free) which recalls ALL agents (I'm not sure if sector wide or empire wide) back to the palace so they can be assigned again.

My main motivation here is to remove the player's urge to move every possible unit every possible turn. I mean, you are an emperor, not some lame manager in a big corporation, there are so many things you can do at once, and you need to rest too. So, the emperor would be limited to how much stuff he can do per turn.

Such game would be probably focused on combat and colonization I guess...

Feudal model vs dictatorship model:

Both would work with the concept above, anyway I could go 2 routes here.

1) Traditional dictatorship model. Not much to say here, the players owns & manages all his planets, builds there every single building, moves every single unit.

2) Feudal model. There are 5 noble houses serving the emperor. Each has their own fleet and treasury (very, very simplistic economy model). The player (emperor) controls the imperial planet (capital) and 2 imperial fleets (always loyal). The rest of the planets are given to noble houses by the player (20% of planet's income goes to the emperor, 80% to the noble house that controls it), each noble house owns (and pays maintenance) 1 or 2 fleets. The player can order around these fleets as desired, AS LONG AS THE NOBLES ARE LOYAL or course Sometimes they might decide otherwise and then their fleets turns into enemy fleet and... To be clear, the player would be faced with ocassional betrayal even if he cares about all nobles a lot (some random events would basicly guarantee at least one betrayal per game).

At the first glance the player would want to limit the nobles power, but it's not necessarily the best (still possible) route. The planetary imperial governors are less competent than nobles when it comes to governing a planet, same goes to fleet commanders, the imperial admirals, while loyal, are not the brightest ones. In short, if the player makes nobles too weak he might lose wars with enemy empires/invaders, if he makes them too strong he faces internal problems and attempts to take over the throne. There would be this whole court politics part and assasination attempts of course.

A fixed arrangement of 5 by 5 adjacent sectors with a main core of 3 by 3 sectors makes little sense: peripheral sectors are almost 2/3 of the map, so they are going to be used, and there's no reason for them to be more dangerous than the central ones.
Instead, you could have variable-sized sectors (presumably star systems) connected by some almost instantaneous gateway to specific other sectors: pseudonatural tunnels (e.g. Star Trek Deep Space Nine), artificial structures (e.g. Transcendence), places where the jump drive can be activated in a certain direction that happens to be aligned with a star system, or something of the sort.
This arrangement has a number of advantages over sectors that can be entered by simply flying very far:

• You can arrange your sectors as any sort of strongly connected graph, possibly nonplanar and with one-way links. For example, you can put sectors along "space roads", or make "hub" sectors with unusually many links.
• Gateway endpoints can be important places to conquer in the sector map, and they allow much better strategical planning than expecting any kind of invasion force from any side of the map.
• Assigning multiple FTL links to the same endpoint or to separate (and possibly distant) endpoints is another interesting kind of variation.
• Sectors are actually separate places, not arbitrary borders on a map.
• Peripheral sectors are actually far from the empire capital: out of telecommunication range and requiring more jumps.
• On the other hand the capital (or the Emperor) can be moved without awkward limitations as long as you are able to reach sectors.
• Maybe the player could build gateways; both cost and usefulness might be hard to balance.

A fixed arrangement of 5 by 5 adjacent sectors with a main core of 3 by 3 sectors makes little sense: peripheral sectors are almost 2/3 of the map, so they are going to be used, and there's no reason for them to be more dangerous than the central ones [...]

Yes, the sectors would be used, but less. As for "no reason" there is no problem, I can make up a story There could be nearby enemy alien empires next to the border and they target the border sectors more. Or there could be more space pirates or nasty space anomalies, or space monsters or automated defences set by long extinct alien races... Anyway, I think it would be good for gameplay if the borders were more dangerous.

Do you find any problems gameplay wise with sectors arranged this way?

As for the rest you wrote, bear in mind I struggle to find a TRICK that would let me make this game with very low budget and very fast, I can't afford to attempt making a full blown 4X game. Still, I want it to be much more fun than an average 4X game

The whole concept of sectors came because I discovered a nice mechanic that is both very convenient to the player (a tiny minimap in the corner and where you hover the mouse over it the main screen quickly changes to show the desired sector) and very easy to me to code (no scrolling, no zooming, no nothing, just a plain single screen displaying rather big planets). Things like variable-sized sectors are out of my budget

I also realized, when I was reading what you wrote, that I hate all wormholes/FTL/navigation thing (for that game). I would prefer if these do not exist in that universe or at least were not mentioned. I want to avoid the Star Trek mood. I would rather go for Dune style folding space which no one knows exactly how it works and no one cares because they have more pressing matters like who is going to backstab them

As for sectors being arbitrary lines on the map, I find it OK... I mean, look at north america's map, there is a lot of these there and it works I think for that game sectors should be more like administrative divisions. Like holding people (planets) that think alike, that rebel similarly, have the same group of local pirates lurking around and having the same sector governor. Althrough, it might be something about geography too... still, that's not a priority and not an absolute requirement I guess.

What I try to figure out is "lines" between planets. For eastetic purposes there HAVE TO be some lines/routes diaplyed betwwen planets in a sector (otherwise it looks like some balls floating on the void). I need some purpose for these routes...

The most natural would be a network of movement connections.

Another thing is how should you move between sectors (again, I don't want scrolling of map). Warp popints is the only thing I thoight of (which I'm not too big fan of).

Big thanks for replying! It's nothing more annoying than talking to yourself :)

Here is the screen of sectors interface (when you move the mouse over the minimap on the right the main screen changes to the sector under mouse, when you move back it changes back to your previously selected sector, when you click on the minimap the selected sector changes; no scrolling or zooming of any kind needed and the planets can be BIG).

I think the non combat focused thing is desirable (some people like the concept), but when we come to details "the goal is to produce a resource intensive wonder as fast as possible" it is unthrilling... In contrast "lash a mayhem across the galaxy conquering other pathetic races" seems much more interesting and fun

Is it because war is inheritably more fun or because we miss something? Or maybe it is only my impression and you find "building a resource intensive wonder/project" more thrilling than conquest?

I was thinking, what would make me "wow" for a non combat focused gameplay and I found so far only one case. Intrigue. The assassins trying to take my life, usurpers trying to overthrow me from my beloved throne and court intrigues of my courtiers (which rarely benefit the empire or me). I mean, if I were to play as an emperor I still need a thrill of some sort. I like economy, like it a lot, I think most games focus too much on military/combat and I don't like it too much, still... If I were just to build an empire in a SimCity like style... I don't know, I feel something is missing there for me.

I wonder if the lack of wow for non-combat building comes partly from lack of risk and choices. Combat's filled with lots of little, potentially dramatic decisions that move between victory and defeat, which typically are very visceral experiences. But what's the victory and defeat of building? Cost overruns or delays aren't probably very dramatic, but what if we're talking about mega-engineering or terraforming that can have disasterous consequences? Or, at a more granular level, what about forcing tradeoffs in the fashion of moral delimmas that create consequences down the road for the rest of your empire? Imagine, as an example, that you have a colony near failure with rioting population that creates a labor shortage. Maybe you can decide to negotiate, or nerve staple them, or open the door to AI and automation, each of which potentially sets a precedent laden with future risks. Maybe negotiating weakens the economy by setting the expectation from other colonies of greater entitlements, while nerve stapling fuels recruitment for rebels and future acts of terror, while AI control potentially risks transforming the colony into a man/machine hive of "others" right in the midst of your empire.

It's definitely not easy to make non-combat match the spice of combat, but I think part of what needs to happen is that it can't be the stuff of deadly dull accounting. It has to fire the imagination.

I wonder if the lack of wow for non-combat building comes partly from lack of risk and choices.

I would argue about choices (I fequently feel the economy/building part of strategies give me more options than combat), but there is no doubt about lack or risk. And I think that's how it is. Even if we do some artificial things like rising the stakes with terraforming and a society at the brink of starvation (which is more about rising the difficulty level than rising emotions level) it would not work... That's simply not the strength of the building gameplay. And let's face it, economy/management/building/industry in the end and in its core always will come to being an accountant... :)

Conflict, that's what is, and basicly always will be, missing from a peaceful economic growth of an empire.

I think we too much try to stick to war vs economy. There are other options like intrigue, internal politics/issues. Intrigue could easily deliver the risk and conflict of military/war level or even higher... The question being how to make a strategy game with focus on intrigue :)