For simplified game play, Brad has stated that we will be about to upgrade all of our ships within our influence. No need for shipyards. However, if you can upgrade all units at one time (via an upgrade feature), that will probably allow for the "bug" of upgrading front line ships that are out of your influence. Otherwise, you won't be able to upgrade all your ships at once, will you? That implementation will be interesting.
Realistically, the more ships that use the same components, the cheaper it is to maintain that component, by item. Economy of scale. So, if you have 1000 ships, all using Scanner Mark 1, that spare parts for Scanner Mark 1 would be very cheap, Maintenence wise. If you only have 10 ships with Scanner Mark 9, that will be some costly parts. Until you get nano-manufacturing and the ship can just take it's biowaste, toss it into a NanoVat, and have the nanites make the part for you.
Of course, realistically, the futher a ship is away from a supply point, the more costly it would be to maintain. So, 20 tiles out (using a 3 Range component ship) would cost you more to maintain... until, once again, you get Nano-facturing and then can make anything that they have the info (blueprint/patterns) for. Then maintenence costs drops to the same, wherever a ship is. And whatever its parts may be. So long as the ship can replicate it's own. Realistically speaking.
Is it worth it to have a game that goes so flat for maintenence and supply costs? Consider that you get nano-facturing in mid game in GC1 (and I don't see them dropping the tech out of GC2)... At worst, you'd need to upgrade your old ships to have a "NanoVat" to get the x1 cost (rather then what it was before).
What's the down side? Realistically speaking, if GC ships use some form of material for energy generation, then once they have Nanofacturing and the pattern/blueprint to that material, a ship no longer has range restrictions. It can supply itself with everything it needs, but trained crew. Unless you are using some form of manufactured crew members. Say, AI constructs in artificial/mechanical bodies (and we start off with exactly such a race! Wow! Let's steal their basic tech!). Now, you are only limited by communication (always instantaneous everywhere in GC; probably use quantum entanglement) and encryption standards. You don't want your enemies instructing your war fleets to decimate your own worlds or head out to Andromeda. However, using quantum entanglement communication devices, the enemy would never be able to send an order to your ships unless they capture your HQ's communication center. And if your enemy captures your HQ, you have bigger problems then your ships being told to head for the dephts of the universe.
Humm... so... realistically speaking, it doesn't take much in GC universe for you to get 0 cost ships with unlimited range, unlimited ammo, and unlimted crew. So, why bother with any cost? Realistically speaking, your Nano equipped ships could drop off a few "nano bombs" on convenient free mass (such as all those rogue planets, asteriods, and comets that we know are floating about, or just your enemy ships without their own nanotech), and replicate themselves. That would yield unlimited ships to attack your enemies. Whoops. That would blow out the game, wouldn't it? You'd have two strategies then... crush your opponents before they get NanoFacturing, or rush for NanoFacturing yourself, and then swarm your enemy. Doesn't sound fun, does it? No super transcendance victory. Just get Nano, and the game is done. NanoGendon! Drop nano bombs off to make fleet swarms, and run some nano "FTL" cruiser missiles at your opponents home worlds which are programmed to rebuild them, and everything on them, into your image (or an image specified by you).
I think we should leave
reality out of it, and only consider what is
fun. After all, FTL starships tends to blow the realism factor.
In the vein of
"what is more fun", is it more fun to have the amount of ships you have linked to empire size/treasury, or based off a logistic tech number multiplied by galaxy size and world commonality? Should you need to research a higher level of logisitics tech to get more ships or shift some of your various worlds infrastructure over to money/logisitics generating structures to be able to afford more ships? Personally, either way works for me. But I think that making it purely a matter of money will allow for better scaling for all map sizes and world commonality. And it means that you are back to the old "bread or guns" decision... do you spend your money on domestic (bread) matters or on military (guns)? If you go into high tech ships with high maintenence costs, you won't have as much money available to pay for all those domestic items like entertainment networks, stadiums, etc etc etc (all those things to keep your people happy). And by going money, it means you can customize your fleet to your needs.... swarms of small, cheap craft, or a medium amount of mixed cost ships or a much smaller number of high cost big ships.