User Registration Costumization for Multisite

Hello

I have a multiste install and want my prospects to be able to create their user before they can create a site. This is for marketing reasons.

The process will be:
Create User >> Choose Blog Template >> Create Site

I want the following:

-The idea is to have the user registration displayed in a Pop Up. I was recommended to use “WP Register Profile” for this. This plugin works, but assings a user to the main site as a subscriber automatically.
-I want users to be automatically logged in and redirected to the “templates” page so that they can create their site.
-I want newly created users to NOT be assigned to any blog. Currently, they are being assigned as subscribers to the main site. I don’t want this.
-I would also like to give prospects the opportunity to create their users with Facebook and/or Google+

What do you guys recommend?

Thank you!