That looks super!
He-he, I was mislead, even twice. 1. I thought that you were talking about animation skeletons (Bip01) not about NPC-skeletons. 2. I thought that “breaking” was taking place in a battle e.g. copping off subsequently an arm, a leg in a melee combat (breakable doors/walls).
I guess this might not work with skinned meshes. Anyhow, I am very curious to see “how it is made”.
is it possible to make the bones crumble slightly at different directions
That look fine for me and very “natural”, a sort of rapid degradation/decomposition, “life” is leaving these bones and they are falling apart.
giving the final axe swipe to a guy and sending him flying
Well, MW death animation sequences are random and not dependent on a weapon/spell used. It is possible to script that in certain cases but a global solution could be tough.