Correct me if I'm wrong, but are the bodies reactive to further shooting while "rag-dolling" after the death, but before they come to rest?
*IE. can you shoot a torso or limb (and have it react to the impact) just after they die, but before the body hits the ground for the first time? (Like when you see gunfighters shoot tin cans, and keep them in the air between shots.)

I would think that Death animations (and there should be dozens) that turn over control to ragdoll chunks in the end would be best.

But I'm divided on the idea of further (in-progress) reactions to attacks. I'm a bit partial to the animation playing out undisturbed; but on the other hand it makes sense that they react when hit with a bat/club or gunfire, and this should change the animation.

In Fallout 4, maybe the death animations could be managed with Havok behaviors? (and have the fixed motions accept additional force from weapon impact?)

I don't really know enough about it yet, but that could be cool if it worked.

Gizmo, have you played Left 4 Dead (1 or 2)? If you blast a zombie in the gut with a shotgun, he will engage his death animation by falling forward slowly, by first falling to his knees and then forward. During this time, you can shoot him some more, he'll still be just as dead, but he'll react to each gun shot impact while initiating his original death animation. He will still fall forward, and he'll twicth some when he's hit by bullets again. It looks pretty realistic.
Edit: it's something I remember playing old MoH many years ago, and there's a death animation that a german could make. He holds his stomach with his hand, then pulls it up to his face and look at it for a second before he falls forward. It's a cool animation, but it looks weird as you are emptying 30 rounds of .45's into him with your Thompson. He's just standing there, non-reactive to your bullets.