Animatable Radii of skin modifier.

So I Love me some skin modifier Buuuuut in trying to use it to animate plant growth (for which its IDEAL!) I discovered that there is no way to animate the thickness or Radii of the verts. So ideally being able to keyframe the x and y radius would be great. But also implementation via Shapekeys would be great AND/OR vertex group weights Perhaps one map for the x one for the y which could then be controlled via VertexWeightProximity and vertex weight mix ?

I think this feature would be super powerful. As is I'm relegated to cheating it with a smooth modifier and some patience.