Right to Rule, i loved that feature in Warband, even though it wasn't that difficult to raise through your companions, it was a stone in your shoe that prevented you to rise to power too soon, in Bannerlord there's no such thing, you can take over the entire thing without a word being said.
I guess you can call RtR politics and that is what this game need right now, it needs more soul.
Increase relationship with lords and ladies when you fight with them or rescue them in battle, another Warband feature that i sorely miss.
Different successions for each kingdom rather than having all in the game following the same, it's too simple.
War attrition, from fight but also from traveling into enemy terrority to make strategic positions on the map count, Sturgia for example would be a lot better off if the Empire and Khuzait had attrition from traveling through their snowy landscape, important stuff.
The base game is still lacking in terms of gameplay mechanics, if they focus on console too much i know where this game will end up, in the garbage bin unfortunately.