This is going to be a silly/weird one, but is there a way to switch nudging buttons from arrows to WASD?
It would feel natural to use the touchpad with right (for selection) and the nudging with left hand using WASD, not unlike in an FPS.
I don’t think that this should be the next big thing (and that we would have to sacrifice the annotation/scale hotkeys), but would be nice to try it out to see if it actually works – although it might not be worth the effort in the end.
Two problems:
Have you considered a game controller or creating your own controller? Haven’t tried it myself but there are some people who built one.
Well, I would give up the annotation and scale shortcuts in a heartbeat if it really works. But I do get the combo key thing since those might be even less ergonomic with WASD. Hadn’t thought of that before.
It’s interesting to consider building a controller as well, but secretly I was kind of hoping you’d say that sure, it has already been done before.
So it was more of a shower thought, but I appreciate your response anyways.
Thanks!
Also consider that these things need to work with the mouse as well, which again speaks for the combo key approach.
Theoretically you can repurpose any input to a certain key combo, e.g. shift-ctrl-opt-up, but I would not recommend it for a plain key. It will too often be in the way. (Perhaps the keypad?)
The geek-out thing to do would be building an Arduino controller. 
could try Keyboard Maestro