Indeed. And on top of that we have the Lisa UGen, which does much of this out of the box and which was made by Dan who is also both a programmer and a musician playing more traditional instruments.

I suggest taking LiSa for the core of the system and once that works looking into analysis to make any transformations on the original material or whatever hybrid-techniques you come up with "aware" of factors like pitch, note onset, zero-crossings, etc.

Inspired by Nick Collins's papers on breakbeat-cutting I got into starting such operations with a analysis stage and I'm never going back. He primarily talks about things like transients for beat-detection but there is no reason why that perspective couldn't be adapted to deal with pitch or any number of other factors.

Assuming you can keep the latency down you can give commercial pedals a real run for their money in this field. I'd be tempted to look into a expression pedal (not just switches) or perhaps a accelerometer bolted to the guitar itself to control parameters beyond a simple on/off. I'd also try to keep the graphical feedback to a bare minimum (if anything) and instead focus on trying to create features so so simple (yet powerful) that this isn't needed.

Go for it! Ask questions! Post sounds!

Yours,

Kas.