I think a great addition to this game or a future GC3 game would be the notion that ships in space can't sit indefinitely. That is, over time they will need food, fuel etc., I'm not suggesting a new level of micromanagement with keeping track of food on a ship, but that eventually any ship will have to return to a friendly planet or star base. The basis for the return could be anything, I simply suggested food and fuel. The time a ship can go without going to a planet or star base perbably should depend on hull size and be some thing like a few months for smalls and like a year or more for large and huge. Or more since friegters have to travel many weeks at times and during the colony rush some colony ships have many weeks sometimes to reach far off planets. If ships don't get resupplied tyhe will autopilot to your nearest planet or starbase
LIfe support modules that are already in the game could be changed to extend the time a ship can stay in space as well as its current duty of extending range. I almost never add life support to my ships but may want to if this were implemented.
Ships in fleets brings up a question. Could be that a ship may have to break out of a fleet to resupply if the whole fleet doesn't want to go to a star base. Or maybe the average of all ships in the fleet could be used; kinda like they're sharing. This would give the option to have a ships along thats unarmed but has a lot of life support, making it a supply ship. Anotyher part of this is having to "reload" after a certain number of battles.
Perhaps being adjacent to an Ally's star base will have the same effect, giving a good reaspon to even have an alliance; other that simply for the victory.
This idea will add a new level of srategy to the game, where as ships can't just sit fot 400 turns. It will also give added meaning to life support module, star bases and alliances.