Blending between two skeletons of different proportions

Let’s say I have two skeletons, one for a child and one for an adult. The bone hierarchy and naming is the same but the length of individual bones are vastly different. Is there a way to blend between them somehow so I can get a result which is for example 40% toward the adult end?
We currently have around a 100 bones so adjusting every one of them in an animation blueprint with Transform (Modify) Bone nodes seems like a bad idea.