I've no personal interest in this project, though I think the idea is excellent and really hope it does go through here and have aimed to provide some feedback from what I think I have learned.
I think the most important point is that an abc does convert to midi but the reverse need not be true. We have been through much of this before... To sumarise, abc is based on music notation and with projects like the abc plus project, abc can also handle words well. MIDI, was never built to do that it is built on the idea of sending signals like play this note for so many miliseconds now. (MIDI is great at what it does BTW).
Another notation possibility Mudcat may like to investigate is Lilypond. It's something I've never had an "in depth" look at but think can do more than abc. My own opinion is that using it would add complexity where there is no need but it has to be said the Yet Another Dt site which offers more in terms of formats than the current MC version does use it...
Whatever, best of luck and good wishes with the project,