trying to add new factions is probably only a waste of time. From the .com FAQ 28.9.

Q. Did the 10 new factions mean that they pushed the factions limits, adding 10 more to the limit ?

A.There are a maximum of 21 factions possible in the game. In Barbarian Invasion there are 10 new playable factions and 11 non-playable factions. Although it is a map of Europe the factions and regions are changed as the game has moved on 300 years or so from where RTW left off.
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