There are so many factions which can be included so I that CA will raise faction limit to 30.
Current list certainly misses muslim factions.
Several factions can be split up into two:
like:
Spain - Castile, Aragon
Holy Roman Empire - into dynastic lines: Habsburgs, Vitelsbahs, Luxembourgs etc.
Russians - Muscovy, Novgorod
Turks - Seljuks, Ottomans (they are not the same!!)

Aslo would like to see more diversity in cultures. So far it seems very western-european.