Or another idea along these lines might be to have a checkbox on the application that says "Submit to audience choice if rejected" and, if they don't get in, those applications are opened to voting by HN users above a certain karma threshold. Pick the five highest ranked applications and bring them in as a normal YC company.
Aren't you afraid that something like that can be easily gamed? Or maybe voting can be limited to accounts that are 2-3+ years old and/or Karma greater than n.
I like this. An alternative would be to have borderlines ranked by those who got into YC in the current round or in past rounds. Top peer ranked would get in just under the cutoff. HN sounds even more exciting (probably couldn't include the whole application, maybe just a company description -- although that might not be something people are comfortable with). Either way, I wonder if there is any peer non-YC consideration.