This is exactly what I'm saying too. Make it feel atleast that some border regions or mountain regions have an identity special to it's own.
For instance the Khuzaits should have more traditional Turkic and maybe more Rus and Syrian peoples within certain zones. Maybe at it's farthest east Indian or Tibetan.
The Aserai would share these Syrian populations, have Armeniac and the Bedouin present in merc trees and maybe Ethiopan/sout
hern nile civilizations maybe Berbers, Morrocan, Songhai.
The Emprie would have caucaus populations Armenian, Georgian and Bulgars, Rus, Syrian and of course the turkic tribes (probably the Khazars or Kipchaks?)
Vlandia can stay vlandia Western Europe, maybe more iberain and italians and possibly some Moroccans/Berbers.
Battania is it's own animal.
Sturgia would of course need to differentiate more between Rus and Nords. Have the noble be Nords with Rus Princes maybe other baltic cultures, Like Lithuanians. Pechengs etc.