Seems there are some people here who might have an answer to this.
What can be used to dissolve cured epoxy?
What can be used to dissolve a thin film of cured polyimide.
Unfortunately, the maker of the polyimide thought I was nuts for
wanting to dissolve it and told me that nothing will dissolve it.

OK, if nothing dissolves it, what will de-link it? Will UV light do
it?
Could strong UV light be used to soften epoxy so as to be able to get
better adhesion to a later layer?