I prefer to keep it simple. Empire, Rebels, CIS, and Republic and just add natives to each planet to help or attack from wookiees, geonosians, gungans, kaminoians, ugnaughts, etc. Adding something like Jabbas goons on tattonie from barada, nitko, gran, rodian, trandoshan, etc.
"You Rebel Scum"
"Wipe them out, all of them"