I will be brief, so as to maximize the odds that busy individuals (i.e., developers with timetables) may glean the most benefit from this.
I feel that M&B 2 could gain a great deal of depth if it incorporated ideas from a wonderful game from 1989 entitled "Sword of the Samurai" (hereafter, "SotS"). In some ways I think that the developers already did this when they made the original M&B games, but there are more ideas that could be considered. The ideas that I feel would be a great deal of fun incorporated into M&B would be the kinds of interactions (mostly the nefarious ones) that you can have with other vassals. Specifically, in SotS you had the option of traveling the game map in one of three ways: 1) at the head of your army, 2) alone, or 3) disguised as a poor ronin. Upon arriving at another vassal's estate, your options depended upon your choice of how you left your own estate. If you are disguised as a poor ronin, then you have all kinds of fun options upon arriving at the vassal's estate: you could do a mini-game to execute the local tax collector which, if you were successful, could incite local rebellions from the peasants, and bring both dishonour (used similarly as "reputation" in M&B) AND weaken his army. If you decided to sneak INSIDE the vassal's estate, you had the option of either kidnapping a family member for ransom, or you could attempt to assassinate the lord himself. Note that you could execute these actions against vassals of your own faction (if you wanted to do plays for power), or they could be vassals of a different faction. The choice was yours. One of the really cool things to keep in mind is that other vassals could and WOULD do the same to you! Sometimes you would find yourself sleeping in your estate and you would be awoken by shouts and it would put you into a mini-game in which you have to either save your family member from being kidnapped, or yourself from being assassinated. It would often come down to a final duel between you and your potential assailant (itself its own type sword fighting duel mini-game), and sometimes you would be heartbroken to find that the assailant was someone whom you thought was an ally, but wanted to take you down/out for their own advancement!
For 1989, SotS was (in my opinion) an incredible game, and it certainly has many wonderful elements that could be incorporated into M&B in a manner that would add an IMMENSE layer of engagement, immersion, and fun. I would urge the developers to please consider adding (more?) elements from this classic game into M&B 2, if they haven't already.