This is the only way I see to add a new user to a blog in a network:
- The user signs in at the root blog to create his account.
- A super admin uses Add a new user at ms-sites.php?action=editblog&id=x to assign that user to blog x.
- The individual blog's admin can then modify that user's permissions if they need to be different than what the super admin specified.
Is there any way to do this without requiring super admin intervention?