Main Blog & Account Center

Okay, I'm not sure exactly if this is possible....

Can I have the default blog that visible to public XDomain.com be a portfolio website and have another subdomain as the Pro-sites Blog?

Essentially I'd like to use another theme to display the work we've done on XDomain.com using a specific theme, but make all Prosite customers use another blog ID# (subdomain) such as "account.XDomain.com" to access/update their prosite status. Is this possible?

I assume I have to update what is the root blog in the wp-config? How do I set the blogID for pro-sites management (i.e. the new URL to Update Prosite Status)?

Obviously I know I can blend the two themes together, but I'm intentionally avoiding this right now because I want to avoid having to troubleshooting a lot of issues getting both to work together... I'd like to see if this is possible first.