Deform to pickup a previous version of the mesh shape

[probiner]

Imagine I have a character to which I keep changing the shape and giving attributes to components. Say at the end of iteration 8 I look at it and find I had the model proportions of an area better better at iteration 6. What's the best way to deform the current character's mesh to a previous iteration so I don't lose all the attributes I build up to iteration 8? Mesh topology and pose will probably be different. I just want to pickup a shape or even blend between them, but shape keys seem to get broken after some editing.

Cheers