Basically you want the game to alternate between a Mount and Blade battle simulator and a small scale combat RPG. While this is possible, I don't think it is desirable to go full RPG with dungeon crawling, while leaving your army garrisoned.
Years ago I thought about how to make traveling the map more interesting and came up with the idea to spawn temporary, generated locations (farms, dwellings, small woods, a waterfall...) in your line of sight that you can visit and some scripted event would happen there, that might involve a small-scale skirmish, exploration for loot, or even a beginning of a larger quest.
That way if you are traveling around and are bored, you will get a chance to do something different for a change. If you are busy and just want to get from A to B fast, you would ignore those locations and they will vanish once out of sight.
