1. bandit playthrough implementation - recruitment, take over hideouts (and upgrade) and street gangs, more loot from raiding, friendly bandit parties can follow you, also: black markets.
2. Feasts - Ai lords and player to have the ability to hold feasts pretty much like in warband, with some fixes already mentioned throughout the forum.
3. More diplomacy options - more ways to interact with other lords, ai lords seeking the player for tasks, more ways to influence others.
I think these are what i like to see the most, short-term-wise.