If you could add just one more faction it would be...

[ColdPrecision]

BULGARIA FTW!
Yeah, I'm of Bulgarian Descent, plus they played a role no smaller than the Serbs in Medieval times. Hell, Byzantium at one point was paying tribute to the Khan.

[ELITEofWARMANGINGERYBREADMEN88]

I would Say the Swiss or The Teutonic Knights..

[BaldwinIV]

Teutonic order is created in 1190 and their country established around 1226. It is impossible to put them into the vanilla game because it starts in 1080

[Darsh]

Maya faction

[Guillaume le Batard]

Abbasid Caliphate of Baghdad!

A little more complexity in the lower right-hand corner of the map would be quite cool! Imagine the old Calipahte, minus many of its former provinces (taken by the Fatimids), still hanging on... until the Timurids show up and start knocking them around!

As a big fan of "the Turks" I would love to see a little a little buffer between me and the inevitable Timurid invasion... heh

Guillaume

[Martok]

As BaldwinIV has already pointed out, however, the Teutonic Knights didn't emerge until well into the period that Medieval 2 covers. Therefore it wouldn't make sense to add them as a starting faction, anymore than it would to add the Timurids or Golden Horde.

Maya faction

Adding the Mayans also wouldn't make sense, as none of the "American" factions are playable (and rightly so).

[Kavhan Isbul]

I am obviously biased here, but the problem is that Bulgaria reappeared on the map in 1187. I just wish that the MTW periods concept was not abandoned in M2TW . Sigh.
From the rest of the options, I believe the Cumans would be the best addition, as they can fill in a huge gap, occupied by rebels, from what I have seen. They played quite an important role in history, so thei inclusion in the game would be well justified. However, the thing I like most about the Cumans is that they simply present another option to the player - with them you have the choice to play a pagan faction, with all advantages and challenges paganism presents, and this would provide some nice variety in what is an already heavy catholic-oriented game.
At the end, however, when which faction is included in a game or not is a decision based not as much on history and even gameplay, but on marketing. And I cannot blame SEGA for that - they need to develop the game for markets where it will sell, otherwise there will be no game at all. I personally rely on the modders - there were some excellent mods for MTW, and I am sure there will be even greater ones for M2TW.

[ELITEofWARMANGINGERYBREADMEN88]

As BaldwinIV has already pointed out, however, the Teutonic Knights didn't emerge until well into the period that Medieval 2 covers. Therefore it wouldn't make sense to add them as a starting faction, anymore than it would to add the Timurids or Golden Horde.


Adding the Mayans also wouldn't make sense, as none of the "American" factions are playable (and rightly so).

Though, you could always Have them as a Unlockable Faction Though..