No, formations and equipement are based upon the way of fighting in that particular area, the era or time you are in; and with your most common enemy. The cohorts were flexible while cohesive, yet the invading armies took a toll on them and it was abandoned because formations became less important, and strategy became dominant in the battlefield.
Unless you have seen both the parthians and the celtiberians develop both falcatas and horse archery, idependently; then my point is valid. Imagine parthians with falcatas and celtiberians with hordes of horse archers.
Tactics are also more adapted to your environment. Like the ambushing germanics, horsemen of thessalian hills, nomadic steppe horsemen, etc.
Nor is pettyness and self-importance either; but hey! I have em. Along with possibly someone else.
Also; here's an anacronistic example of how awful a hoplite shield wall is with underarm spear holding
https://www.youtube.com/watch?v=x4RFr...eature=related