BuddyPress.org

Would this allow for the main site to not be a BuddyPress site but the main WordPress MU domain (www.mydomain.com).

Then when a new blog is created it would be it’s own buddypress private social area, lets say for company XYZ.mydomain.com.

Then employees from XYZ could come to XYZ.mydomain.com and register from there?

This is what I’m trying to do with my requirements I have. If we are looking for the same thing maybe we can help each other and forward the answer to each other when we find it.