After https://pagure.io/fedora-infrastructure/issue/9617 , I think it might be a good idea to not delete project right away just tag them "to be deleted" with 1 or 2 weeks delay (and hide it), then have a task to clean the old projects running on a regular basis.

This way, in case of user errors, a sysadmin could just switch 1 bit in the DB to recover it.