I went through the mod's dedicated page and realized a number of problems.
1. It is a mod kit, which means it has to be extensively revised and further developed to be integretated to a mod like crpg. Needless to say it is too much work.
2. It says in the notes that the kit adds dismemberable npcs to bandit and raider groups in native single player. There is probably no good way of implementing it throughout the entire game. If you watch the video, you will realize that there are indeed differently modeled npcs there. They are exclusively coded to be dismemberable.
3. Looks like almost every hit is capable of tearing apart a limb. In the video again, see how a bandit's arm comes off in one slash every single time. Big big problem there. What is going to happen to shielders? Actually, players say that the torn hand continues to levitate and hold the shield. Think about what kind of glitches it would cause with 2handers or polearmers.
Ideally, it would be a good choice to randomly tear apart a limb or behead a player only after a killing blow (the last hit) has been inflicted. Then again, although I am clueless about coding stuff, I can tell that it would take a lot of time and be a huge pain in the ass for the devs, especially when their time is extremely valuable for their upcoming project. But I think devs could think of implementing this in M:BG. It would add lots of flavor. Consider it dear devs.