Here is a crazy idea, kinda like how subreddits on reddit work. Use the separate Launch HN page[0], with just the launch threads (one per company). Put the one that is currently at the top on the main home page (or maybe two, or maybe treat it like a stack and pop the top on a regular basis skipping ones that have already appeared).
That way people who are interested in launches (like me) can check out the launch page, but everyone else will still see the most popular launches. Then you don't have to guess which ones will be popular.
Maybe once a week have an automatic summary thread for all the ones that didn't make the home page similar to what you describe above, with one per comment.
As for you being the editing bottleneck, why not teach the partners how to do the editing so they can be the first step, and then maybe you just do a final pass after the partners have hopefully mostly gotten it good?
That way people who are interested in launches (like me) can check out the launch page, but everyone else will still see the most popular launches. Then you don't have to guess which ones will be popular.
Maybe once a week have an automatic summary thread for all the ones that didn't make the home page similar to what you describe above, with one per comment.
As for you being the editing bottleneck, why not teach the partners how to do the editing so they can be the first step, and then maybe you just do a final pass after the partners have hopefully mostly gotten it good?
[0] https://news.ycombinator.com/launches