Buddypress and Member Blog Integration

My site is intended to be a similar setup as Etsy, I'm using Buddypress, WP Multisite, and Marketpress to get that functionality just need it all to integrate the same as it does on Etsy. The look I want to achieve with my site is to have new member blogs/sites/store appear as if they are part of the site not an entirely new site with it's own theme.

I am having a hard time finding out how to do this if at all. Does anyone have any suggestions on how to go about this? Any plugins I might need to look into etc? Or am I pursuing a hopeless cause.

Thanks in advance.