Scenario: I have a functioning single-site install of 3.0 with a few thousand users. I am creating a multi-site "member" install that is linked to this one. (I'm sharing the users table and cookies etc for seamless login)
Need: I want to grant access to the new site to a small group of users. They can be picked by a) user meta flag, OR b) role/capability, OR c) whatever.
Trick: I don't want to restrict access to certain pages / posts, but EVERYTHING including Buddypress, and other internals.
In short, is there a simple function / hook that says: only allow logged in users with some flag access to the whole site.
Thanks for the advice