Going back to the method cut/copy/paste and UUID regeneration: we had some discussions over here... I think the best way would be to always regenerate the UUIDs when pasting methods, no matter if they have duplicates or not.
It's easier to get what is happening and would avoid more import problems. Not sure though if we can then still allow what Patrick described (moving code in a hierarchy of forms and keeping UUIDs) as that could work fine at import - but only if the forms are in the same module. Otherwise it could still cause problems during import. And if you cut - save - paste into another module (even inside a hierarchy of forms), at the moment of the paste we no longer know if the pasted method was from the same module or not to automatically do the correction only if it's needed.
So in short case
SVY-10940 was reopened to always regenerate the UUID of methods on paste in order to avoid such problems and I created case
SVY-11100 to investigate why import didn't fail nicely. A sample solution for SVY-11100 would help if you can send one.