I would definetly want to include kind of "Italic Faction" to make it challenging for the Romans to advance/keep control of Italy.
I would include a kind of "free people" faction, to represent not hostile, but independent Greek colonies like Massila, Syracuse etc., instead them being rebells to grab on...
I´d like to have an Egyptian native faction ( a counter faction to Ptoleys ), who would annoy the Diadochi and get an opportunity to overthrow them ( perhaps i could try to realize this plan with Saba invading the south of Egypt and inpiring Rebellion there, but i´m not sure about the culture penalties )
Celtiberians are a must, imho, and hopefully will be included in EB II( while i am pretty sure the other mentioned factions won´t ).
Thats what comes to my mind instantly.
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