I recently watched Kingdom of Heaven for like the third time, and it reminds me of Mount and Blade so much that it forces me to play it right after it ends. In comparison to the movie mount and blade is only missing a couple things.
Which you have pointed out: People get old or die of sickness. Where in mount and blade you never get old, nobody rarely dies.
Villages/Castles. In the movie the main character owns a piece of land and goes to work on it to make it prosper. In mount and blade the most you can do is ask how the village is doing and the typical remark is "We are short on hands but we count our blessings" How nice would it be to actually have you and your troops hang around and actually make the village prosper. Then maybe you can build walls around it, and who know's slowly upgrade it to becoming a main Castle or fortress.
This brings up fortresses and Time; Fortresses really have no use other than fighting. I mean it would be nice to have some sort of trading going on. I mean i see farmers routing to em but what is really the point? And then there is time. When there is a feast i tend to beat all lords to the castle, and the only way i can have em all in the hall is if i run around outside till they all make it to the fortress.. come on now
I've also been playing Kenshi recently and thought that an adaption to the games mechanics would be really awesome in M&B. Building your own little village from scratch, Training dummies to train troops. Along with having a Lineage/Family so it doesn't seem like you live forever would make this an ultimate sandbox game. Which is why i love M&B, so far it's the best Sand box game i've played with infinite amount of possibilities. Some minor changes would make Bannerlord the only game i'd ever want. And if they let out a couple things and add it on as DLC i'll be okay with that.