I would personally say the max size for a “desktop“ 3d printer is 60x60x80cm because that size is quite big and small enough to fit on a standard desk or heavy duty workstation the h3 series I think should be 60x60x80cm on the outside without an ams and should be 512x512x512mm build volume and be as close to a 3d printer from a professional environment and be brang to the masses.
Shipping becomes an issue after a certain sized box/weight and that is also a consideration.