[JR]

How about:
1. Fighters that can be sent on missions away from their bases/carriers instead of being confined as they are? It would be nice to be able to send a swarm of fighters into a system ahead of the main fleet to soften things up before an invasion.

2. A larger playing field with more than 255 stars - say 500?

3. Neutral, non-spacefaring races, in various stages of development, that can be added to one's empire by either diplomatic persuasion or conquest?

4. Military bases on planets that troops can be stationed in without having to treat them like cargo with the appropriate room for cargo? Any invasion would have to conquer these bases before anything else? The bases should also have upgradable defenses.

5. Research modules for space stations/starbases, that would add to total research, and would/could contribute to a specific type of research if located in say, the same system as a black hole? This one could contribute research points to energy production/gravity research.

6. Power plants for space stations etc? Everything needs a power plant. Even one that could be knocked out prior to a takeover of the station.

7. The addition of cities to planets that would house the population. The more settlements/towns/cities there are, the more population on a planet.

8. One planetary government center per planet. Without which, a planetary governor cannot be appointed. This would also affect planetary population morale and stability.

9. A way to retreat from the combat screen instead of survivors being confined to the corner until oblivion occurs?

I have oodles of other suggestions but they'll be held back for another time.