Give people bonuses for controlling more of galaxy? That way everyone will want to take away small factions' land to get bonuses, rather than using them to take out large faction? Also adds realism.
I think technology should be more elaborate. Like for specialized research facility with high price and upkeep. You pay to do research and then have to store it in database built and run by your money, you can get better mexes, longer range, etc from various research. It also has PW struct upgrade research, like better mines. If database is destroyed, technology is lost and must be paid for again in research lab. If it is captured (maybe by cons reclaiming it ingame, or bought, give suggestions), then all the upgrades in database he has that you don't are transferred to you, and maybe also let them have a few turns to research other upgrades he has at lower price because you might be able to use database to hack into other ones? Each research is player only, unless player spends more money to make it public to his faction. Other factions can also try to break into databases? This can scale forever? Also, it gives incentive for players to take planets rather than helping other factions so they get money for research?
Whenever a faction loses all its planets, its gone, and the players are, maybe taken in as slaves and give money bonus to whoever owns them and the players can only first person units and owner can detonate them with click if they try to kill own stuff? This will inspire players to eliminate factions as quickly as possible so no help weakest, just get the weakest out of my sight so I get their tech, PW money, and IP and they stop bothering me?
