Complex Wordpress, Multisite, Buddypress, Marketpress site

I really need help with a wordpress site I'm building and apparently I'm out of my depth, as none of the solutions I come up with are working. If anyone could help, or maybe point me in the direction of someone that might, that would be great. Thanks.

Here's a brief description of what I'm trying to do:
Wordpress multisite with Buddypress and the MarketPress plugin for ecommerce.
I'm building a network of bloggers, each with their own store.
All the user blogs need to be managed by one admin (to rule them all). That way I can give them access to certain things and hide other things. I'd prefer if the users could administrate from the frontend (ala Buddypress), however, that's not absolutely necessary. Maybe I could just theme the wp-admin area.
I'm using the Marketpress plugin, mainly because I need the percentage ability (chained paypal payments) that it offers.

If anyone has any ideas to offer, from start to finish, what plugins, themes, hacks, etc, that might work to accomplish this project, please help. Very much appreciated. Thanks.