I agree with you completely Springman, it would be ideal to integrate sound with the other functions of the TCB. When I started this project things like the Teensy and its amazing audio software resources did not exist, not to mention my abilities were untested and my knowledge very limited. Much of what I have endeavored to do is proof-of-concept. Although I see now it can all be made to work, I did not know that at the beginning, I could only proceed at each step as far as my abilities and existing resources would allow.
If we were to re-design the project from the ground up starting today it would take a different form, but my hope is that the development and proof-work that has been completed thus far can be built on by others.
PJRC released in late 2016 some incredible new development boards called the Teensy 3.5 and 3.6. Either of these could form the basis of an advanced control board with integrated sound, and probably cost less at the same time. Ultimately one would want to create their own board, but the fact you can get them so cheaply in breadboard compatible format makes them extremely easy to prototype and prove with. Code would need to be ported and the sound functionality integrated into the TCB firmware. This is a major undertaking but there is no question it could all be made to work with resources now available.
So there is a lot that could be done, and a lot that would be great to do. But all of it takes time and energy and there is no money to be made from it, so volunteers are required. For now I'm focused on seeing the TCB released with all its limitations and possibilities both. If a community can be created around this project as a result, then sky will truly be the limit. Otherwise it is hard to see a way forward for a Mk 2 design. But I agree with you it would be great to get to that point some day.