As long as it is possible I disband and roleplay, but for factions like sweboz, Lusotannia, phavla and saka rauka its impossible. Even with force diplomacy you have to conquer a lot really fast.
I hated it to beeing forced to conquer whole iberia by 250 or most of the seleukid empire by 240. Its ahistorical, impossible (From where do I get the people to rule and coordinate everything...) and bloody.
Still I think its great EB offers so many different experiences depending on the culture you use. I just hope in EB the partians arent a Blitzkrieg faction anymore