Maybe plus a way of decoupling parts of the grid from the slots entirely.
So the simplest thing I can imagine that for a custom grid you can define up to 3 rectangles that each map to a synth slot, and use the slot’s midi channel and scale settings. In addition, you can define for each remaining pad (that is not covered by a rectangle) a note number and a midi channel. Maybe aftertouch on/off, too, or for the adventurous even also a MIDI CC instead of a note.
Is that what you’re looking for?
Thanks for the thoughts. I don’t use midi much and this sounds more complicating. I’ll try and draw up the sort of layout I want, but that will take time.
On the Artiphon Chorda I found a way that could make each pad capable of playing two notes depending where it was touched. I don’t want that two note per pad thing, but what I did do is to make the top of the pads play the scale as the preset was set to play. The lower part of the pads could play a note a semitone below (or a semitone higher - actually they could be set to play notes a fifth or even an octave above). This way I could easily play in the scale, but all accidentals were easily available - so effectively chromatic. Something like this could work for all modal scales the same way as long as they only use tone or semitone intervals. Instead of different areas of pads the adjacent pads would give the accidentals. A chromatic scale layout comes close but it’s still not so easy to navigate.
Actually, it just struck me with only 5 rows the layout I was thinking of is a bit too limited - it might be better to deal with a chromatic scale instead. I’ve had an obsession with trying to emulate duet concertina key layouts for so long it’s distorted my judgement! Maybe, one day, I’ll come across a machine that will bend better to my strange desires.
Hells bells! my brain wouldn’t switch off and I’ve just thought of other layouts that would work better.