Also tried to prevent units from using their secondary weapons by negating their secondary attributes, IE changing values to 0, no, none etc. This did prevent units from using their secondary weapons, so did appear to be an alternate option.
If you do that they´ll still use the phalanx spears, not the one of the actual model and they´ll hold them either straight up (and seem to be punching with their fists) or the spear keeps the formation though the soldier does not. At least, that´s the case in 1.2, I haven´t yet tried it in 1.5, but I suspect some similar result.