Can't wait for this. I don't think they'll fuck it up.
M&B is amazing but could definitely use a new engine. So much of this one is patchwork improvements built on something 2 people put together in a turkish basement. Even getting Warband out was a small miracle since the game was never designed for multiplayer.
I doubt they will fuck up the modability, these guys know what's up, they relied on modders to create all the games' content. If they are published by Paradox again it will be doubley since they are the best publishers for mod support.