Actually, you can do this with the copy skin weight feature.
All you need to do is make a duplicate of you model (with 'duplicate input connection' option checked so it copys the model, skeleton, and all the skinning history with it). Afterwards the new copy is going to be your smooth skin weight reference. I suggest you put the duplicate object and skeleton in a new layer and hide it.
At this point you can detach or do whatever you want with your skeleton or your model. After you are done, reskin the character with smooth skin. Then unhide your weight reference model and skeleton and do a 'copy skin weight' from the weight reference model to the one you want to copy to. In order to use the copy skin weight, make sure both of the root joint are aligned, otherwise it wouldn't let you copy.
Also, try to preserve the skeleton hierachy as much as possible. With different hierachy, it will still copy, but results might be a bit off. It is a good habit to have the right skeleton structure from the start anyhow.
Hope this helps.
