Oh, and I did discuss this with Robert via email, and he took at the Nemo source code and had this to say:
The second problem is that it looks that Nemo’s 4-track interface is indeed hardcoded into the sources, at several places. So tweaking this could result is a lot of problems, testing, debugging, tweaking, etc. While of course it would be possible to change this (I’ve done major surgery in the Octo source tree), it is simply too much work for me right now.
Regarding this first issue, I believe all that is addressed in the development document available for downloading. (By addressed I mean: they walk you through the solution, but you still have to do all the labor.)
The second is suggesting that it will be a bit of work. But think of double-capacity Nemo! Imagine the glory! TAKE THE CHALLENGE.