Nice design - and no reason why it shouldnt work. One criticism if I may; the Z-configuration of the Y-motion belt will be problematic. its inducing a rotational moment on the z-axis which loads the bearings on the high side more than those on the low side. This will wear the bearings unevenly and could result in cantilever stiction. I would redesign that to put in another jockey pulley and make the y-motion belt flat along its length .