So I would like to suggest a few things:

For the Turkic peoples:
-add Azerbaijani to the Turkish culture group
-change the name of the Tatar culture group to the Kipchak cultural group
-change the Mishar culture to Cuman because they lead Cumania
-break the Altaic culture group into Turkestani and Mongolic

For the Mongolic peoples:
-transfer Oirat, Khalkha, and Korchin culture groups to the Mongolic group
-transfer Mongol culture to the Mongolic group, but renamed to Ordos
-transfer Buryat to the Mongolic group
-add a Yuan remnant state in Oirat / Khalkha / Buryat lands

For the Uralic peoples:
-change the religion of Perm from Slavic to Suomi
-change the name of Suomi to Suomenusko or Ukonusko
-transfer Sami from the Nordic culture group to the Ugric culture group
-change the name of the Ugric culture group to the Uralic or Finno-Ugric culture group (Ugric only pertains to Hungarians, Khanty, and Mansi)
-transfer Hungarian to the Ugric culture group

For the Tungusic peoples:
-change the name of the Evenk culture group to the Tungusic culture group

Some more suggestions:
-transfer Slovak from the Carpathian to the West Slavic culture group
-transfer Gothic from the Byzantine culture group to the Germanic culture group
-transfer Albanian to a new Illyrian or Albanian culture group
-unite the Japanese culture groups together into Yamato, save for a new Okinawan culture group

This was a lot, but I suggested these changes to be more in line with realism while still allowing for alternate history. I'm very much so enjoying the mod so far and I hope to see great new things come in the future.