Steve, thanks for your thoughtful comments, I know you're talking from experience in this domain.

So "candidate A" needs to be told the truth and confront their limitations, else they will never improve. Candidates deserve honest and unbiased feedback from people who actually do the hiring, not their proxies, but at present there is precious little feedback given.

You make a good point about the size of the market, so I'm not about to sink life savings into a venture. I am however seriously considering spending a few days working up a MVP.