Your project got me interested in what people were doing in the guitar pedal scene, and it's been interesting browsing around various websites seeing the projects and development equipment that people are building. On one site I ran across a reference to a chip called the FV-1. If you browse their website you'll find some discussion of effects here:
I thought that it might be an interesting reference for you. To see how the chip works, and their dissussion of effects at a high level plus some small examples in their assembler. If you see anything really interesting that's a little our of reach you could try to influence Chip to make it possible in the future. Maybe you already know about all of this, but I hope that it's interesting to someone.