Speaking of new factions, if we want something new, we could add the rebels. There are really few rebels in the start, but every now and then some units spawn for them. Theoretically they could be a force to be reckoned with over time if the spanwed units are not dealt with
Could be fun for me too, and we wouldn't need a whole new faction. (Maybe a new mechanic that if taxes are too high, or settlements get sacked or traded for too long you actually get rebels even if you are in "green". Could be done with console commands especially if I'm co-admining, but let's not got ahead of ourselfs so fast)