+1 on allowing a custom MIDI channel per Drum part, like it's done in the BeatStep Pro.
This would allow using all 24 Drum parts by assigning them to multiple drums machines (hardware or software).
My use case is that I have a Volca Beats and a Volca Sample (10 parts each), which would map nicely to a custom drum map, with four parts to spare (to be assigned to a Software drum like Spark for example). Also this would help with the Volca Sample's peculiar MIDI implementation (one channel per part).