As for gameplay I'd like to see ability to split competing factions before switching planets into my own property. 

This could be done by diplomacy, hidden moves as supporting revolutions, spys, events or peace treatys. 

The new split-factions might have same ship style and faction traits (or different as well), but may alter their spirit decissions (benelovent, pragmatic, evil) to fit the player ones instead former confrontation. 

I could see a quite interesting diplomatic enhancement, even for multiplayer games, with split-factions.