Scenario: library uses a reciprocal borrowing patron category and wants to track what neighboring area patrons are coming from, attribute is limited to patron category and mandatory. Patron moves, updates membership to be no longer reciprocal. The attribute cannot be removed while the patron is in a category using it, and the option disappears from the edit form once their new category no longer uses that attribute, but the data is left behind. A workaround is to blank that out with the batch patron modification tool, but it would be nice if, when moving a patron out of a category with a mandatory attribute, Koha offered a prompt to remove the no-longer-applicable attribute data.