Sorry to bump an old thread.
I've been giving this a little thought. Let me know if I'm on the wrong path.
It seems as though the default sound set of the MT-32 could be reproduced as a sound font (perhaps it already has?). After all, the SC-55's MT-32 emulation mode did something similar. What we're really missing is the ability to load custom sound data.
Now for a given game using custom sound data, couldn't a sound font be generated specific to that game? Ultimately, you might have, in addition to the MT-32 default sound font, a sound font for every game that used custom sound data. But, at least when it comes to playing old games, the need for actual MT-32 emulation would be circumvented.