I want the same thing you keep asking about. UVLayout has a pro feature where I can cut up a shell anyway I want including multiple pieces and then I can select that shell and copy all the similar shells so their uvs match the one I have cut up. If Rizom would add this I'd switch to using it all the time, without it I can work faster in UVLayout. It sucks because Rizom has better packing and straightening but the inability to copy and paste uvs from one shell to another is entirely frustrating. Copying cut selections to meshes before cutting simply isn't enough, sometimes meshes are complex and need to be taken apart into multiple sections or cut up uvs need to be adjusted. Making post cut changes to each mesh is simply not the answer. Cut once and copy is the best solution. I keep checking back every so often to see if the feature has been implemented but it just doesn't seem to be a priority.