Intellijel Scales is part of my setup because it allows me to constrain pitches to pre-set groups (e.g. "pitch class sets" or "PC-sets").
The basic setup is like this:
1. get a Scales unit
2. read the manual to know how to program your own pitch selections (PC sets) into Scales
3. use "Pitch B" to SELECT WHICH of up to 7 PC sets is currently active
4. use Pitch A input as the pitch signal quantized to your selected PC set
5. use Pitch A output as your quantized pitch signal to send to any units needing it
I send a sequencer signal to Pitch B to pick a PC set on a defined rhythmic plan (e.g. I'm setting the "harmonic rhythm") of the song, then I send any signal to Pitch A to pick pitches from the active PC set.
This setup allows for huge flexibility while at the same time constraining output pitches to a desired sequence of PC sets. Super useful for my purposes. It lets me do things like:
-- I find 3 chords I like in a sequence. I program those 3 chords into Scales. Then my modular can jam / riff / do arpeggios in ways that exactly fit that chord sequence.
-- ditto but programming in scales that fit with a chord sequence (as suggested by the "chord-scale theory" common to Berklee books)
-- I will be evolving this technique to allow "auto-counterpoint" though that is trickier in practice.
In summary, I think Scales could be a good fit for your need, specifically because you can change the active PCset via PitchB input. In a guitar analogy: in Scales used this way, PitchB is like the fretting hand, PitchA is like the strumming hand.
Good luck, enjoy!