Ad Sharing Plugin?

I am looking for a plugin similar to WPMU’s Ad Sharing but instead of me setting the ad that is shared on the contributors blogs I want the contributor to be able to run their own ads, maybe submit ads in a section to be approved for use in their blogs this way the contributor doesn’t have to wait for each ad to be approved when they add a new blog post. Maybe the plugin would also let me sell ad space and it would give each advertiser their own area to log in to and see their stats, add their ads for us to approve and etc.