Theres also "clans" or "families" within factions, so maybe the same could happen with them. They dislike other families in the faction, alliances form, civil war starts, etc. Would be cool. Would also be neat to be able to confederate with factions so like if Vlandia split in two for a civil war, the losing side can be confederated by the winning and it would end up being a pretty natural civil war scenario.
Maybe even the empire could reunite ¯\_(ツ)_/¯