I like this is idea, but for for dlc or expansion rather than the base game for a few reasons:
1) You will be able to achieve this in effect through custom factions.
2) It would require many more art assets which it seems from comments on the stream are a major bottleneck for Stardock.
3) Currently factions are defined by traits, bonuses, and tech trees. I'm not sure that any of these make a ton of sense to attribute to a leader. The racial bonuses make the most sense, but are also the most generic.