That looks good to me. As far as the art is concerned, do you think Steppe should be less saturated? The overall transition from plains via steppes and semidesert to desert looks alright. What if Steppe uses the Semidesert art and I come up with something inbetween Semidesert and Desert art?1 hammer, 1 gold next to river, 1 food next to river, all improvements, +x% to improvement construction speed, some bonus to light cavalry (movement? attack? pillaging without losing movepoints?).
So, with steppe belt somewhere here -
View attachment 499573
- steppe east of Volga river is mostly untouched (farms are harder to built, and barbarians more threatening, but nothing too extreme), but Southern Siberia is seriously nerfed: cities still can be founded here, but their growth will be delayed until Chemistry and labourers, and even then they will need huge amount of work.
I also see what you mean with the transition from Steppe to other terrains. I think this is related to what is prioritised to be drawn if two terrains border each other, so that might be an easy fix.
About stats, I am somewhat concerned how Steppe compares to Semidesert. Shouldn't it be better than Semidesert?
Khazars are just too shortlived to be the center point of an entire civ in my opinion. You don't think the Golden Horde should be in here somewhere, appearing in case the Mongols collapse? They are of course nominally a Mongol polity but in Russia most of the people under their rule were Tatars and they were referred as such by Russians. The Golden/Great Horde would be a good obstacle to Russia and is the predecessor to the other Khanates you mention.Bulgars -> Kazan/Astrakhan Khanate -> Tatarstan/Bashkiria, or Khazars -> Crimean Khanate/Nogai Horde -> Northern Causasus states and ethnicities.
First (Volga) variant provides more serious opponent to Russia (sudden rebellion in middle of empire), but Bulgars are less known and less interesting as PC civ.
Second (Pontic) less challenging for Russia and less historical, but Khazars (Judaism state religion, at last!) is more interesting civ.
Don't think a lot, though.