Ragdoll only for specific limb

is it possible to make only certain limbs be ragdolls, while the rest of the character's body is still animated?

as far as i understand, this should work like boob/hair physics where they simply aren't included in any of the animations

but this means that i would have to make multiple copies of animations for the cases in which a certain limb isn't supposed to be animated

i'm using mecanim, and i've tried using an avatar mask, either for the arm, or for the rest of the body.

if the avatar mask is set to the arm, unless i have some animation for it, nothing happens

if the avatar mask is set to the rest of the body, the arms are in the t-pose, but the rigidbodies and character joints don't work

with the legacy animations, there's a bit of code that removes the animation keys of a specified transform from an animation, but this doesn't seem to be available for mecanim, since we can't access the actual animation state via script

 AnimationState.RemoveMixingTransform(Transform)

is there any solution to this?