This might be difficult to administer. Nobody smart stores users' passwords directly, so it's not like they can list different passwords with their associated permissions on a page. If you go with user-selected "nicknames", then do you require the app to use the nickname too? Or do you just compare with all the hashes on the user's account? Maybe instead the app has to pass a hash of the perms themselves, serialized in some canonical way. How many users can figure this out? I've known DBAs who couldn't figure out analogous situations.
Even so, you're probably right in the long term.