Now that I understand, I still don't get why the model doesn't change to use current YTM instead of interest rate. Seems like the same logic would hold -- comparing how it is priced to its default probability to find notes that meet whatever hurdle rate you have set. But I may be missing something
Also, a bit of unsolicited advice. I somehow think this current offering may come back to haunt you. While it's noble you are making an effort to meet customer demands, if they don't acutely understand what these suggestions are and are not they may fault the entire model for being broken just because of user error. May be something to consider