In reality significant settlements didnt exist on the steppes in this period. If there were a way for a province to exist without a settlement in it...
A big departure from how the game normally works, but it would be realistic. Settled civilizations, as in reality, would be hard pressed to hold on to territory there because there would be no "power node" to conquer.
A "nomad type province" would be owned by whatever faction had the most forces in it. Nomadic factions would have a huge advantage in controlling these provinces because of how quickly an all cavalry army can move, and their style of warfare. If as a settled civilization you wanted to conquer the steppe you would have to build forts to control borders, keeping the nomads out.

Of course, the game engine probably dosnt allow for any of this.