The need at 50,000 ft is to have private content only available to authorized (read: approved) users.
Within that, the client wants to be able to limit access to certain pages to certain users. For example, each user would have a "dashboard" page what would be updated by the site admin and only the site admin. In addition, there might be another page(s) where multi-user could access. For example, "Agenda for tonight's meeting".
I'm not sure if there's a need for allowing users (read: non-admins) to update a wiki page but there might be. At the moment it's about distributing access to content and limiting who can see what, when, etc.
Thanks in advance.