I think it's fine just to have people submit proposals, getting the proposal approved, and then creating the content and having the final post approved, rejecte

I think it's fine just to have people submit proposals, getting the proposal approved, and then creating the content and having the final post approved, rejected, or getting suggested edits. This could either be done by the mods or by some sort of rotating panel. Then the final content could be treated like the jobs postings, where there is a separate tab for preflighted content and it lives on the front page for at least some minimum amount of time, longer if there is engagement. It could also be interesting to try something like Edge.org, where different people create content around a given question or theme.