Admins: how do your users join private usergroups

[dsmcd01]

Hello, my company is asking that guests be disabled and registered users have permissions to one set of 'public forums'. Then, if the users want access to a set of private forums, they need to provide additional personal/occupational information to our supermoderators, and if the request is approved the supermods add the private usergroup to that user, thus granting access to the private forums.

Essentially, the user needs to go through a 2nd registration process. This seems a bit unwieldly and difficult to automate.

I'm curious how other admins manage already-registered users requests to join private usergroups. Any comments?

Thx,
D.