I don't see why you should shutdown the rest of the site to do this. What's the benefit of not having a discussion section or restricting the total number of posts? The problem as I see it has nothing to do with the total number of posts, but with the fact that there are not many high quality posts. In regards to your second point, couldn't you just do something similar with the existing promoted section. It should be fairly easy to set up an email address for people to submit potential promoted worthy posts and a group of reviewers who will review, select and post one article a week.