As fixed equipment, it's not ideal, but it's not nearly as hamstringing on the Turkina Z as you are making it out to be. Even less so for the Osteon and Dire Wolf. Are the extra two hexes of mobility you'd get with IJJ nice? Sure, but 3 is just fine in a pinch. Hell, 3 hexes is the short range for HE rounds anyways-and it's just one less than what you need to get out of minimum range for both of the other main munition types.