This would solve one of the biggest problems I have with split keyboards; where do I put my mouse? At least I'm using a Logitech Ergo Trackball, which means that I can predictability move from the keyboard to the mouse, but there is no easy way of positioning a keyboard like the ErgoDox EZ while still comfortably using the mouse as well. I ended up switching to a smaller Razer BlackWidow Lite as it allows for a more comfortable keyboard-mouse workflow for me.
I put a trackpad to the left of my keyboard and taught myself to mouse with my left, as well as right, hand, and it's been a big improvement. Right hand is still stronger but my left hand is now functional for many tasks.