Is there a way to unconvert a lead?

Summary:

We have an unusual request from a user who wants to know if it is possible to "un-convert" a lead once it is converted to an opportunity. To the best of my knowledge, if a lead is converted they would need to mark the opportunity as lost and then create a new lead. I do not know of any native functionality that would reverse a conversion, and do not know if there is any way to customize that process flow to work in reverse. Does anyone have any suggestions or ideas on how that might be accomplished? I do understand