BuddyPress.org

@NrFive That was the layout of the BuddyPress parent theme pre-BP 1.2. It’s do-able but not easy as A-B-C.

== every user created blog to be part of the main site ==
It can be as simple as making your blog a multi-author blog in a single WP install. But even if you go multisite, you can achieve the same look and feel by creating the child theme and just changing main navigation in header.php to get navigation of main site with BP.