Approving new sites and keeping sites private until 'published'

I need strict control over the new users signing up new sites. I need to gather information from them, but not set up the site until approved. I would think this would be pretty necessary to prevent spam and misuse. Is there a plugin for this that is MultiSite compatible? I've seen some regular WP plugins but not sure if they are what I am after:

Would really like to stick with WPMU plugins.

Also is there a way to let them sign up and start setting up their site, but keep it offline until further approval. Or at least some kind of offline mode I can look into customizing?