I see what you are saying now, thanks for the explanation. This looks quite complicated, so I don't think I am going to be implementing this in the near term. The addon is open source now and I will accept PRs too. So, perhaps someone else can implement this, or someone else can be commissioned to do this.
I looked at: https://forum.babylonjs.com/t/animation-blend-trees-part-2/1185 and https://docs.godotengine.org/en/stable/tutorials/animation/animation_tree.html