How to have animation ignore bones?

I want to make a character have an active ragdoll, but only on the head.

I've tried to use Avatar Mask to not allow it to control the head, but all the Avatar Mask does it prevent the animation from moving the transform of the head. In other words, it can't rotate.

What I want is for it to totally release a hold of the transform so my character Joints and rigidbodies can work.