Firstly to the Bannerlord team: Good job on fixing (fingers crossed) bankruptcy of NPC lords.
Secondly, here are a few suggestions to further improve the game's economy and overall feel of the game:
1. Banditry is prevalent with low prosperity. This makes sense upon taking a new village/castle/town. It would force you to take care of your new area (NPC lords included) and earn this back. As prosperity rises, however, banditry reduces to the point of 0 at a high level. Yes, 0. Chasing down bandits is tedious as is knocking out bandit camps. This should 100% tie back in to recruitment ability but inversely. At low prosperity villagers are desperate for work and you can find a plethora of tier 1 recruits. As the prosperity increases, you find very few troops but the ones you do find are tier 4+. This is on a slider so it can run the entire gamut. This would also tie in to esteem with village notables. I think there should be fewer quests available but they give a great deal more reputation if completed. This way, early on in the game, a player might actively choose to seek out villages in their preferred faction to get those better units. Of course with less money, they'll likely be frugal.