It wouldn't necessarily be very difficult, but I do try to take ideas like these and apply them in a more general way. Otherwise, it becomes a one-off feature and I definitely try to avoid those.
What else would one want to edit en mass? Modifying the nickname, first name, last name, address, etc, for a set of users almost never makes sense (unless you're trying to delete certain information for all of your users). Out of curiosity, why do you want to modify the Notes for a set of players all at once?