Tried it again and it works!
I have a few suggestions for units if you need inspiration:
Germanic Cleavers: 2H axe unit with frenzy.
The Silent Fangs: Also a Germanic unit that has those wolf helmets and can ambush like Iceni Ambushers. Got the idea, imagine them hiding in tall grass or bushes with those wolf pelts, would make a lot of sense.
Armored Indian Elephants for Parthia: Those cool ones that Seleucids have.
I will think of more if you want.