Since these admins are temporary, I wouldn't even bother with adding them to users.ini. Store them with a method of your choice (nvault, SQL, etc.). When the user connects and he has temporary admin status, call set_user_flags() with the appropriate flags. With nvault, you can set the timestamp to his expire date and when he connects after this expire date, you can remove the nvault record and not give him admin flags. This would essentially be an entire re-write.