BuddyPress.org

This may be a unique case, but it’s worth asking.

I am running a WPMS installation at ultrapowa.us, and I was wondering if there was a way I could set it up so registration and activation, as well as all the main BuddyPress features were accessible from a subdomain, say profiles.ultrapowa.us. That way my main site would be ultrapowa.us, and all Multisite domains would be subdomains of that, but registration and groups would be on profiles.ultrapowa.us. Is there any way at all to set up a system like that?