The APIs and Inkscape based software use the same motion control code– there is a difference in how you can control it, but not a difference in the smoothness of motion.
At a minimum, you’ll need to modify the configuration file as well, to set the limits and resolution.
One other approach that you could possibly use would be to substitute
doXYMove — This moves as
<AxisA> + <AxisB>, and
<AxisA> - <AxisB>. I’m not sure that the signs are right (you might need to invert one or both), but it will rotate the coordinate system by 45 degrees.