I’m not sure what you’re getting at regarding the button colors being a problem. That’s how all other piano rolls are designed, and it’s never been a problem.
Also, fine-nudging should work quite well while holding ctrl when mouse warping is on (xypad). That’s how you get sub-pixel precision of move movements. Having a square xypad isn’t that fun (needed to circumvent weird x/y mouse speed), but you should be able to crop it and do the maths needed.