Here is the factions that I would like to see in MTW2

CATHOLIC

Aragon,
Castile Leon (Spain),
Crusader States,
Denmark,
England,
France,
Holy Roman Empire,
Hungary
Milan (or Genoa),
Papal States,
Poland
Portugal,
Scotland,
Sicily,
Teutonic Order,
Venice,

MUSLIM

The Turks,
Egypt,
The Moors

ORTHADOX

Armenians
Bulgarians
Byzantium,
Kiew Russians,
Novgorod
Serbians

PAGAN

Aztecs,
Cumans,
Lithuanians,
Mongols,
Tumurids,

Some factions could change, if the game does not have era's (Crusader States, Teutonic Order ect.). They should be replaced by muslim, pagan, orthedox or other exotic factions other than catholic.