You mentioned that units have a set of stats that never change. Is there any type of advancement (automatic RPG-style, new equipment, heart container collection, buying upgrades with gold/credits/cash, etc.)?
Indeed, what is the vector of advancement of the player? Is he present in the battles as a character, or are only his troops depicted?
How do you hire/acquire new units?
All units are named characters with a backstory of some sort (like Shining Force). The general idea is that, as you progress through narrative, you will encounter various people who wish to aid your cause and will join you. In many cases the people that join you will be somewhat dependent on decisions you've made, and there will definitely be "secret characters" that can be found in secret areas or through quest chains or what-have-you. The set in stone statistics are the primary way in which I intend to practically differentiate one character from another, along with the advancement system I've designed.
Characters will have a kind of skill grid in which to distribute points as they level up. I'm calling it a quadrant system, and it works like this. A quadrant is a 3x3 grid of skills related to a given category. So one quadrant might be 1 handed weapons, while another might be nature magic. Each character will have a set of 4 quadrants in which to place skill points (which gives them a 6x6 skill grid). Exactly which 4 each character gets will be somewhat related to their stats.
I intend to have two other smaller systems that influence development. Firstly a "weak" class system, ie rather than a class that determines which skills you can advance in, have the skills you advance in determine your class. So, for example, if you put 2 points in sword, 2 in shield, and 1 in healing, you would be eligible to be a paladin. Being a paladin might get you a special defend skill and a bonus to healing or something like that. At any time a character might be eligible for several classes but has to choose one.
Also, I am hoping to include a trait system (this will get cut for time though I'm sure). You could think of this as character level achievements that would grant small passive bonuses. Maybe you complete a quest where a character becomes famous a great swordsman, well now that character has a 5% bonus to damage with a sword equipped.
How do you intend on messaging this? It feels like it could be confusing.
The best implementation of a related system I've seen would be in Radiant Historia. I recommend you have a look if you're not familiar with the title.
I will look at Radiant Historia, as I haven't seen it before. Before I get into how this works I just want to say that I've thought a good deal about how to keep this as simple as possible. It is a little on the complex side but I don't think too much so. I think in this case the complexity is worth it, but as with all things, if testing says otherwise I have no objections to reworking it.
My implementation so far is as follows. Characters (and enemies) have a speed stat of 1-10 that will, for the most part, be static throughout the game. Characters then have an initiative score that is calculated very simply by 20-spd... Why 20? Well, its arbitrary and its just a starting point, but using 20 will allow the fastest character in the game to get nearly (not quite) twice as many turns as the slowest, which seems good to me as the start of the balance process. Combat is then divided up into rounds.
So lets take two characters, one with a speed of 9, one with a speed of 5. That translates to initiative scores of 11 and 15 respectively. Character A gets a turn every 11th round (so, rounds 11, 22, 33, 44, etc) (EDIT: Line changed in light of post below). While character B gets one every 15th round (15, 30, 45). So in this case, character A would get turns 3 and 4 (33 and 44) before B gets its 3rd (45). It's the initiative score that I am thinking about adding the weight dynamic to.
As far as displays, the most basic thing is a turn order bar showed prominently on the combat screen. Even if you ignore all the specific numbers, at the very least you should be able to see at a glance the order in which things will be getting turns. In addition, I want to have tooltips over every number which will allow a player to see where that number came from. When you hover over "initiative" it will, perhaps, show you "20 - 8 + 2 = 14 (20 - Spd + weight modifier = initiative)". If possible, I'd like to have the turn order bar numbered (with rounds) and have unit cards slotted into the appropriate place, but a lot of this depends on aesthetics so I'm going to leave that decision until later.
This depends on how you plan on using terrain. If your mobile units can easily access the higher ground, and it gives them +20% damage on their ranged attacks, they won't necessarily be weaker even if their weapons are. Before long, they can decimate their enemies while keeping out of range too easily. On the other hand, if terrain is largely unused, or only prevents mobility, then the absence of a strategic advantage will make it not desirable to have mobile units.
You have to strike the right balance to make this viable, and terrain interactions will be key.
Well, terrain is something I would love to do more with, but I feel like I'm not going to just based on all the other things I'd prefer to spend my time on. There will definitely be mobility effects from terrain, and one thing I do absolutely intend to include is skills and spells that modify terrain in some way (though this may end up being the ability to summon and/or place walls on the map).
I'd go against that personally. You want players to make decisions. If one decision creates a sequence of 'things', its not as fun, and the strategy depth is lost on the player.
Counterattacks can be interesting, but they shouldn't be the norm. Perhaps there are conditions to be met, or special abilities to have. I can see a pikeman having the 'first strike' when an enemy comes in range (kinda like Overwatch in X-Com for example) but if every unit gets to retaliate when attacked, they don't really need to attack themselves, just make sure they're the painted target.
I'm leaning in that direction too.
A few other notes, but I have to get back to coding... lol. I will probably include a damage type system... I like it and I think people in general have a good understanding of how that works these days. I'm still hashing out the particulars though.
Characters will definitely have an armor score of some sort. I'm thinking about the possibility of having additional armor slots open up through the use of skill points, not sure about that one yet. The basic idea is to very simplistically subtract the armor from damage, thereby making heavily armored targets more resistant against highly mobile units that are going to hit many times for small damage, and more susceptible to heavy hitters.
Cleverness (I'll probably chance the name, cleverness doesn't sound so great) is intended to govern things like stealth, backstabbing, thievery in general. I'm also thinking about including trap skills that would fall under this stat.
Again, thanks for the great replies!