Be sure to back up any work your doing because it might crash maya if you try it. I am not responsible for any damage done, thank you very much.
Here's what to do:
1. put the following code in you programfiles/maya/scripts/startup directory. Or whereever you want I guess.
2. Make a new shelf button with the following codelet:
// source script
this will call the script when you press it.
3. This step could crash Maya. So back up work and all that.
Take or make a subdivision surface. Press the mel button you made. What its doing is looking through every uv on the subd surface and establishing a relationship with the corresponding poly uvs. It should take under a minute I hope (depends on how dense your model is).
4. When it's done you'll be dropped into a polygonal copy of the subd surface. Grab some uvs and edit them. Remember you can't cut/merge yet; i should be able to do that today (basically regenerate the whole poly all over again).
5. After you edited uvs, select the polygon uvs that you want to update on the subd surface. Then type
It'll run through the subd surface and update. You can check to make sure that they are the same. Remember it only updates the uvs that you selected. If you forget to select some it'll be out of synch. This is esp true with operations like relax, where it affects everything.
If you don't select any uvs it'll (i hope) update all of them. This, again, could take some time.
If anyone wants to edit this script or use or whatever, feel free, just post your modifications. uh okay.
thanks for your time