Multisite registration page with Pro Sites

Hi,

I'm using Pro Sites plugin for a client.

I'd like to know more information about the registration. My client want to offer a system like this :

- People register on the main site to get a Website (sub-folder domain) ;
- People pay for Premium options (done with Pro Sites) ;

The registration process is defined by WordPress and it's not pretty nice. For instance, it asks people if they want to get an ID or a Website. Same thing about privacy.

My question is : how can I get something similar to this : https://en.wordpress.com/signup/ with Pro Sites ?

Thanks