It's tax prep time, so thoughts turn to updating Quicken. I came across this: https://www.cnet.com/how-to/how-to-convert-your-magic-trackpad-to-a-magic-numpad/ but the company when under.
Then it occurred, put a simple grid on my trackpad and use BBT to map the keys to locations on the trackpad.
BTT has mapped corners and edges for input; why not the entire trackpad and allow the trackpad to be 'gridded up' with different sized grids and assign each location a single or double-tap gesture?
This would allow not only a keypad overlay but also all kinds of interesting configurations.