Is it possible for one of the Islamic Altaic states in European Russia to survive and become a powerful nation? How powerful? Would they conquer Siberia? How far would they get into Christian Europe?
What would the outside effects of a Muslim, Tatar 'Russia' be?
The problem is demographics. Changes in climate and agriculture will definitely put the Slavs on top simply due to their location, so you must address this somehow. The steppes won't stay dominant forever.
I like this idea, and am considering something like it for a project in the works, but it is a difficult thing to achieve, no matter how awesome such a state might be. I do suspect that it could rule atleast much of what is usually regarded in the WEst as Siberia.