Apply different weights to bones in animation

I’ve done an animation system for my avatars, I can choose multiple animations to play at the same time and can apply masks, so for example my avatar can talk and gesticulate while walking.

To do this I’m changing which interpolants and propertymixers are present in each AnimationAction.

What I would really like is to be able to apply weights to each one of the bones, and I was wondering if there’s a way to do it.