You just try strapping that brand new warp/wormhole drive into it and see how long it takes before you turn the crew inside out...

that's the inertial dampeners, not the hull. of course the hull does have to be able to take the internal stresses. hulls are what hold components together. inertial dampeners are what keep the crew from becoming a smear on the wall under high G forces.

you might say that hulls of a given size can only use engines of a certain size due to lack of structural integrity, even if they have enough "slots".

There's more to consider than simple friction even in real non fictional science and it can be made very believable if you have a good writer and like all good lies base it partly in truth...

all of the people some of the time, some of the people all of the time, you know the rest.

remember its a 4x, not angry birds, your target demographic will tend to be a little smarter than the average bear.

its doesn't have to be "realistic", but it does have to be believable within the rules of the game universe.

hull upgrades can go both ways. USAF operates airframes that are over 50 years old (transports and tankers). but the f-111 vs the f-117 is a definite hull upgrade due to new materials. note that both are deep penetration ground strike aircraft. one pre-stealth, and the other post-stealth. this is somewhat similar to the tiger I vs tiger II, where the hull itself was one of the the major new technologies in the design. the t-34 is another example of a "new kind of hull" type design.

the US navy commonly will rip out the entire guts of a ship to refit it over course of many months. about the only thing they can't do is put intercontinental ballistic missiles on a ship not originally deigned for it, and they can probably do that too, given enough time.

there's no reason to think that such behavior patterns would not occur in the future, any future, unless you have game universe rules that make it otherwise.

so you probably only need hull upgrades when you have changes in hull technology - which would most likely be the result of completing a node on the research tree.

by limiting or eliminating changes in hull technology you can limit or eliminate hull upgrades.

If you REALLY want to try something different from what hordes of games have done before, why not start from this as a concept? Represent/build ships in terms of their roles, rather than their surface statistics. If you're the Grand Galactic Emperor, you probably don't want to hear about the Gravlax class cruiser having 16x Generation III long-range plasma blasters and hunter-killer torpedoes... your level of detail is probably closer to "Sir, we are happy to present the Gravlax class cruiser, a combat line ship capable of engaging the enemy at beyond their current maximum range" or "The Shadowhawk class is undetectable by enemies and carries a contingent of elite marines to perform rapid boarding actions."

That's the only role I invented :) If you have more ideas for roles, drop them here.

A quick handful off the top of my head:

- ECM ships

- sensor ships

- troop carriers/dropships/boarding parties

- carriers

- FTL generators/shuttles

- resource carriers/gatherers

May or may not apply depending on your background/combat style, and many could be hybridized.

Lots of military on this list.

What about science, exploration and survey vessels?

Commercial shipping and civilian transportation?