The promotion system is part of the problem here. In the real world there is a lot more difference in the tactical capabilities between a raw conscript swordsman, a veteran swordsman, and a fully armored, professional swordsman, than there is between a swordsman, an axeman, and a maceman. Without embracing fantasy tropes, It is difficult to conceptualize an axeman type unit that would not just be a reskin of a swordsman.