Hi les,
thanks a ton for your 2cents. I think we have the same opinion about it.
With actor.WeldGoals(), I think I can query from python which verts are having a welded nature. I use this information to copy the morph delta from the parent to the child. As you said, the verts wont move for the child if they are welded to the parent.
BUT: I think the normals move still, and this can cause shading bugs.