I did for vanilla, but it didn't involve much beyond improved name files, a few CBs to make conquering pagans something that their neighbours would do in the long run (early game this is prevented by the Warrior Cult auto-building being at original strength), and geographical and historical territory and culture corrections. I'm in the process of slowly updating it to Legacy of Rome, while incorporating Better Looking Characters.
List of changes that I'm porting over:
- Finnish and Baltic Ugric culture fused together into Baltic Finnish culture, with historical areas represented. Swedish names and other later additions removed from namefiles, with more authentic names, surnames and patrilineal names presented (though this obviously does cause problems due to -npoika suffix's limitations with said names)
- Lappish cultural and tribal borders fixed, no more Swedes and Norwegians several hundred miles North of the area they actually inhabitated at the time. Ducal titles in Finland also split better, with the Northern regions forming the new Duchy of Lappland. Thinking about making the Lapps in Sweden, Kola peninsula and Norway Tengriists.
- A new culture added to split the previous Komi culture to more accurately represent the Finno-Ugric tribal groups on the Eastern end of the map, with Mordvins added as a new culture, Komi limited to the North (new previously missing tribal nations added, such as Komi-Permyaks), with Ob-Ugric in the East as a vassal of the Cumans. These groups follow Tengriist faith, Suomenusko has been limited to the Baltic region and ends in Bjarmia.
- In general, the borders in the East are more close to reality now. There were many areas that were presented as part of Russian principalities in the game but weren't conquered by Russians until more than two hundred years after game start.
- I made a special Tribal Unification CB for pagan lieges who possess either insanely high stats, or Ambitious and just high stats. Content blocks the CB from being available. CB allows conquest of provinces that share the specific Culture AND Religion of the attacker.
- Lithuanians got a better version of this, which has notably lower requirements to make the formation of Kingdom of Lithuania easier and more likely to happen.
- Raid CB lifted from Pagans! mod that's now defunct, allows Pagans to attack neighbours for cash demands.
- Pagan kingly titles can only be formed by either pagans or by their culture group. Titles have also been revised, with Kingdom of Finland replaced by Kingdom of Tshudes. Ducal borders have been adjusted in Estonia and Livland.
New things that I'll make after this:
- Events for Suomenusko pagans presenting various customs and laws. Now you'll get to throw bastards into the swamp!
- Decisions and Festivals specific for Suomenusko, such as Karhunpeijaiset.
- Generic conversion option event for Pagans in the Baltic. Karelia and Bjarmian provinces will have a variant of this to choose to convert to Orthodoxy. Only top lieges get this event.
- Trade and technology events for Pagans in Western Europe that allow slight improvement to their technological state. Requires King or higher tier title (or as top liege), and a certain amount of time to pass in the game.