My biggest concern with any melee changes that they could change/add is that the game that we know would cease to be the "easier to learn, hard to master' esqe game. I don't want Bannerlord to have the most realistic attacks or parries in it, nor do I want stances or different kinds of blocks like deflection and hard blocks.
The biggest problem in my eyes with a game that takes into account those systems is that the game starts to lose its simplicity, which makes the game more frustrating to play. Take a game like counter strike: I don't think there's one advocate in the world that will say that it is a very realistic game in any means (what with jump scouting and all that nonsense), but it is a very competitive game which is enjoyed by a lot of players around the world. So, take for instance that the game counter strike over the years becomes increasingly more and more realistic, sort of how some are advocating for the melee changes in Bannerlord, and the game takes into effect more complex bullet ballistics like wind, stamina, iron sights, etc. All of these changes would create a game that is more realistic, yes, but is more dependent on "realism" and not dependent on player skill.
So lets go back to Bannerlord. The brilliance with games which are simple is that imo, they are less frustrating. In a game like Warband, I get frustrated with myself if I lose a melee fight because I know that I was the one who failed because I wasn't good enough, not that the game has some bizarre system which feels strange and awkward to use. For example, reflexes, which every human has and can display in a numerous amount of ways, and the most important thing is that in a game like Warband it feels comfortable to play. Sure, we have to teach ourselves the appropriate response to those reflexes, but those come rather easily because the game is simple. Stuff like a stance system which I would think would feel very stiff to play having to constantly changing stances and then block. Things like weapon glancing, (although I do admit needs to be added to the game in some degree) I do not want simply because It would feel strange for many players and more reliant on those systems rather than a player skills that we can apply in game. In real life, it's very different seeing as you can actually feel the weapon in your hands and where it actually needs to go. However, this is a game, and although gadgets like VR have made some very good headway, I don't believe something like Virtual Touch will be coming any time soon, at least for us consumers.
So anyway, that's my take on all of this. I could keep going but I think I've said what I've wanted to say.
tl;dr
Basically, Warband is successful by being simple, by using mechanics that feel right, and not using mechanics which we can't feel at all.