I'm kind of expecting a 'charismatic rule' type thing for the steppes; with prestige being used as the 'bribe' mechanic that they are introducing for republics (where you bribe with money). I'm just guessing that in the Baltic Sea areas there were probably similar leadership mechanisms; a sort of 'favoured son' situation like an elective monarchy with a bonus to opinion based on being the strongest son of the ruler (which fits nicely with the steppe nomads, for whom I originally imagined the mechanic).
Also, though the crusades showed Europe's dark side, with tons of bloodshed especially at home, it seems to me we're missing a mechanic for any sort of diplomatic interaction between the religions. There should be some in some cases. Introducing a more playable Lithuania (and a Lithuania which has the possibility, in the game, to do what it did historically) situation would expand this part of the game, which can only be a good thing.