For next iteration, consider integrating trackpads? Moving to the mouse and back is pain enough that people go all-in on keyboard-only interfaces. I velcroed a trackpad to the middle of a Kinesis Advantage. Now I use either hand for the mouse, and even stretch a finger or thumb to the pad without leaving the keys. The movement is little different from using the keyboard. But for split keyboard, you'd need one trackpa…
I have a ErgoDox EZ, and I still prefer using my Framework 13 (with Kanata![0]) because having my thumbs navigate the trackpad is so convenient even with a keyboard-driven setup.