Vault robberies and thief skills
In Mount and Blade, we visit the castles quite often. And, as we all know, where's a castle, there's a treasure. Expensive cutlery, furs from animals hunted by the grandpa, and finally gold and jewelry.
What if we added a little bit of stealth to the game and let us sneak to places like that? The case is simple. You bypass/kill the guards, go in unnoticed, pick the locks, find a chest full of gold, and escape without raising the alarm – the treasure is yours. And if it didn't work out, you face prison, death, and all that jazz.
The locations for the robberies are already there, but the developers or modders would have to prepare a lot of different assets and mechanics, like detection cones or the ability to hide bodies, but I believe that would be feasible and would give us a whole new path of development – playing as thief could be fun, especially if we could also pickpocket. And there could be additional quests. How about a lord ordering us to steal a particular item? Or to silently assassinate his enemy?