Some changes for the Caucasus?
Just a few ideas here, not sure if they've been brought up by anyone else.
The Chechens don't really seem to be accurately modeled in VIP. Their population levels are a bit low, with only 67,000 people in Grozny province in 1836. According to The Chechens by Amjad M. Jaimoukha, their population was supposedly close to a million(thought this number seems too high) in the 1840s, and eventually dropped to 140,000 by 1861. It doesn't seem like the fighting in the North Caucasus is intense enough in VIP to match this drop, even if it has to be simplified because of the limits of the game engine. Maybe instead of having just POPs with high militancy to model the war, the Caucasian Imamate should exist as a playable country that is constantly targeted by the Russian AI to represent their territory slowly being chipped away over 20 or so years. I'm not really sure if this could work, though.
The POP in Grozny that would represent Chechens is also labeled as Circassian, and that doesn't seem like the right way to label them, Circassian is a broad term for speakers of Northwest Caucasian languages, while Chechens speak a Nakh language which isn't really related to the other family. I would propose making a new ethnicity called Vainakh, so that the three major language families that share cultural similarities could be grouped together, Circassians for the Northwest Caucasus, Vainakh to represent Chechens, Ingush, and Nakh language speakers in Daghestan, and Daghestani to represent Daghestani languages.
The Ossetians are also portrayed as being Sunni, when there's never been a huge proportion of Muslim Ossetians. Certainly by 1836, most Ossetians would have been Orthodox, though there would be a Sunni minority, and I'm unsure of what percent they would have been.