That sounds like the answer there Ted. The BK series (not sure if the GW could) can have as many Drum Parts as you want, and a MIDI Set can be Linked to each Performance allowing you to direct the Part to the MIDI Out. But you're going to need some kind of external MIDI processor to rechannelize to non-drum channels, as CH10 can only be used for Drumkits (if you are returning it to the BK).

I'm finding MIDI Sets to be very powerful for quickly routing style Parts, Song Parts or live keyboard playing to address external gear. I'm USB-ing an iPad Pro to my BK9 and it's amazingly easy to route what you want to where you want it to go. But you DO need to plan a little bit in advance, as you only get eight MIDI Sets globally (and no way to back them up other than paper and pen!😱).

But put much of the onus on the receiving device, and those 8 MIDI Sets will suffice!