Inspired by https://github.com/classvsoftware/under-new-management it seems like the browser itself ought to watch out for extensions changing ownership, and give users the option to decide whether they want to keep using it.
This appears to be a very active form of abuse right now, where extension authors are inundated with buyout offers from sleazy people/companies who will add in tracking or whatever.
Perhaps this could take the form of automatically revoking all permissions on an ownership change, and re-requesting?