Individual post privacy in multi-site

We have 300+ domains and thousands of subdomains. Basically, you pay to blog and get access to all of the blog/domains. The sitewide privacy plugin works, however it is all or nothing. What if a user would like all of his posts to a particular blogsite private, or just one post in particular he wants private, but otherwise, wants his other posts visible? We are getting a lot of people asking for this. Thanks!