Suggestion - Roles which users are allowed to manually assign to themselves.

I would like an option in the role permssions selections which says "Allow users with roles above this one to manually assign themselves this role." This would be different to the "Manage Roles" privilege as it would only apply to that specific role, they would only be able to assign it to themselves, not anybody else, and they would not be able to edit it or create new ones.

The reason for this is that there are certain things in my server which only some people want to be notified about. I don't want to use @everyone in this case, and if they could "opt in" through assigning themselves a specific role - say, "Notify about [game] competitions" - then I could just tag that role and have everyone who had opted in notified.