Bannerlord improvements from my experience so far:
Forest Bandits; map need to be more linear, calling in 40+ archer buddies to shoot at your men ain't fun or balanced, perhaps more cliffs need to be added like the desert/ mountain bandit camps.
Bandit lairs in general; army should scale to the force faced, having 9 men for a lair filled with 100 bandits is beyond challenging, for every ~10 bandits above 30, 1 man should be added to your party.
Smithing; I don't mind the grind, honestly it's a big money maker, but please give me quests related to smithing that give me a chance to get some of the schematics at random (free a master blacksmith/ help him get materials), or move the perk to unlock more away from the iron/steel/ refining path, perhaps adding books to splurge some money on and unlock weapon parts to smith. (I could go up the dual skill tree with a companion I suppose.. but leveling smithing with one just to unlock schematics and splitting smithing xp between the refiner and the weapon smith would be awful)
A pop up tooltip for party size giving you the requirements for increasing it.
More map varieties, mainly bandit lairs and some more open world I feel it could add a significant challenge/ enjoyment factor by mixing it up.