Sorry for my delay in replying. I (along with someone from the reddit link) did figure out a way to make it work.
We do use set /p. The key is - instead of launching it through config file of DosBox, we launch from the CMD prompt, and call DosBox to launch from there.
Functionally, I could have 400+ entries -- it prompts me for the choice (currently, I can type 1-14, but I could go to any number I wanted) and then - quickly launches DosBox, mounts the drive and launches the game. When I exit the game, it brings me back to the menu.
The person I worked with was exceptional -- beyond being extremely knowledgeable, his ability to explain provided me with an understanding (to the point that I began figuring things out for myself, eventually) -- that's a fantastic trait (and I've told him so).
I realized, early on, the limitations of DosBox wouldn't limit the ability to launch the process outside of DosBox, and then, call the exe from there.