The writers arguing for this (not me, I don't have experience or expertise to have an opinion) say that cheaper airframes are more effective because of slower s

The writers arguing for this (not me, I don't have experience or expertise to have an opinion) say that cheaper airframes are more effective because of slower stall speed, ability to operate at lower altitude, and greater fuel stamina, all of which translate to better loiter characteristics. Also have heard that ground commanders hate the high-altitude planes for CAS because they're less likely to correctly discriminate the situtation on the ground before unloading. To your point -- yes, we don't operate AC208; I think iraq is the only one who does. (And if the sight of a hellfire stapled to the wing of a small turbopro doesn't make you want to run and hide, I don't know what will). But we also don't operate the F-35 in the CAS mission. neither plane is a good example of a CAS plane.