Well I imagine, that it MIGHT be possible to fix with some rod and cogwheels in the keyboard part synchronising the two sides. Obviously the technically super simple mechanism of the Pro1 has this coupling by design by the support being a plate and not two individual arms.
(Actually the mechanism of the Pro1 though very simple in principle once you got the idea, is a bit harder to do with the correct ratios if you try to do the math, it was a bit of a puzzle when II tried to make a program to create the principal gif here)