Does the Organic Groups module family (plus CiviCRM) meet our needs without og_sites?

Does Organic Groups meet our needs?

Perhaps it does, given that an OG team homepage is
already visible without a login. How can this page act as the basis for
developing a website using URL redirection and theme overrides ?

Let's refer to the requirements document for multisite functionality:


Perhaps the question is, What does OG, together with related modules, NOT do for us which we need?