The Endless Legend factions (at least some of them) with all their advantages would, fit into Endless Space 2 quite well. For Example the new Kapaku from Endless Legend would make a very nice part in Endless Space 2 with an affinity to lava planets or even burning gas planets. Especially the terraforming option to turn planets into volcanic hells. I'd find it really interesting to play with (or against) them in Endless Space 2.

I just think implementing some of those factions would enrich the Endless Space 2 universe quite well!