BuddyPress.org

Wouldn’t this plugin cover what we need?

It seemlessly merges posts from an RSS feed with other posts in your blog. If there was a way to selectively offer this plugin to member blogs, that would solve it for me.

And perhaps some integration with Buddypress account areas to make it more idiot-proof; a field where members can enter their RSS feed, without having to go into the plugin back-end.