Thread: Multichannel Quantizers
Gonna throw this out there even though it might not exactly meet your criteria, but I've been considering buying a Crow by Monome to make a flexible microtonal quantizer, and similarly you could make a multichannel one, though given the number of inputs and outputs a multichannel one would require you to update the script to switch scales or change notes.
my tunes: https://stevehand.bandcamp.com/