It would have been great if the early Roman legion was one distinct unit and not divided between hastati, principes and triarii. The legion unit could encompass the three mentioned units, i.e. the first 3 lines armed as hastati, the next three as principes and the last 3 as triarii (similar to M2TW, where the look/armor of the soldiers varied but this time with clear grouping as I mentioned). The same could be applied to other units as well. For example, the first and last lines of a phalanx unit could be armed to the teeth, with bronze breastplates, grieves and the in-between just with linen armor.