Fascinating suggestion!
I'm a huge fan of using micro- & macrotonal scales or historically accurate tuning in software instruments. I wonder if there is any way of applying a Scala type of overlay on the PF scale. I would think that you'd almost have to 'borrow' the HarModulator's chromatic scale, then apply selective tuning to each scale degree in a Diatonic / Quadravox selection.
Now – to address how much user demand would justify the R&D … We're back to the custom scale idea that pops up here often. Perhaps it's something that can be considered in the reported H9-style editor for the Stompboxes. Even one custom scale in the PF could be converted to a blues scale, Super Locrian, or Hirajoshi in a programmable editor environment.
Even if you're uninterested in alternative tunings, consider this: Per-note detuning effects.
With the Mix set anywhere but 0% or 100%, each note played can have it's own pitch deviation in cents. In other words, an adjustable MicroPitch effect that is controlled by the notes you play. It's a killer effect on the software synths that I use.
Not to mention bringing a few more keyboardists into the fold with the ability to reflect an instrument's emulated and actual tuning. I can see where it may be difficult to 'quantize' where any input pitchbending would snap to the next scale degree, though.
