Signup form on subdomain

Need to fix my mind. Wondering if it was possible to use for all the registrations. And for marketing and presenting my site.
This way I can install a single page with a custom theme in and another theme in
Ideal to separate the registration process from the main site and at the same time make the sign up page working.
Because my main site is a premium theme using a slider so the sign up form is causing a major issue with the home page if installed on