[fallingfrog]

I think that whereas most guitar effects are really very simple (gain and clipping, or delaying the signal and adding it back in), this approach will probably work just fine.

But, it is sort of using a sledgehammer where a tap from a spoon will do- the original tube screamer is just an op amp and a couple diodes, plus a bit of eq! Not much to it.

Plus, your real problems are going to be noise level (tube screamers in particular are noisy but a discrete transistor distortion can be made very very quiet). your a/d converter, your power requirements (comparable analog distortion effects use a few milliwatts) and cost.

Edit: But that said, this is a super cool project! Good job! Sorry I just realized that what I wrote was kind of negative.