I would have to agree with you Left Eye. A Turkish faction of some kind should be included. However, it depends on the starting date. If it is before 500, I'm not sure if they could be in. And even after that, they'd have to be the Kok Turks, right? And then the Eastern and Western Khagnate...

So it depends on the starting date, whether or not their could be a Turkish faction in Anatolia (Turkey).
But the Turks had a huge impact in the world, more so than many other places.

Then again, considering how spread out their focus is (American faction? Snore...), then it is inevitable that far more important factions are left out in favor of "fan favorites". But again, it depends on the start date.