This is a bit of an odd question. I do have an idea for a possible site, but before I even propose it I wanted to check if there is something that Stack Exchange software can do (or be updated to do), namely keep posts locked so only logged in users can see them.
The idea is to use the Stack Exchange model for a Writer's Workshop type site. Author can both post questions and stories to be critiqued. The second type of post is the problem, any stories that are posted can not be publicly viewable otherwise an author risks losing their first serial rights (I've been a magazine editor/publisher in the past, so I know how serious this is. My rule of thumb was that if Google can find it, it's published).
So, is this the sort of thing the Stack Exchange software can do?