You left off Dominion. :-D
Also, I was unable to select "All of the Above" - truth being they need a mechanic for "mini-Factions". Rather than just being Warp-Cultures to hegemonize or conquer, make them full systems with a Starbase and ships already there. You can make First Contact, and exchange Trade agreements. This let's you "colonize", and gives access to their ships. But they build only their ships, and thse ships have a different Fleet card maybe to reflect different abilities. They also add new Science cards, tied to their science Node (Vulcan would have TWO).
If an enemy ever shows up in that system with MORE ships than you or the ally have there, the new race decides they're not being sufficiently defended, and switches to the new master.