In my view of bring closer "civilizations" and "barbarians tribes" and fighting ethnocentrism, I would like to open a discussion trying to break stereotypes. Not only for making justice and a game a little more historical accurate, but also cause I think (at least in design documents) that grecoroman civs gets a lot of mechanics and some civs like celts are like "spam a lot of warriors and go ahead".
It's true that we have a lot of information regarding the "civilized" armies, and having standing armies means a lot of effort trying to get diverse estrategies and that imply different kinds of soldiers, equipment, tactics and movement, and also a lot of information about the "barbarian civs" come from roman and greek people, depicting that cultures likes less or more savages.
Regarding gameplay, for example, we have hoplites phalanx. Instead of making an unique feature for Greeks (with Pike wall for succesors and Testudo for Romans) most civs could use shield walls with spearman, and then make a bonus for the hellenic cultures. Cause a phalanx is a shield wall. The point would be having civs like celts with normal stuff against civs that can train artillery, mercenaries (if the concept is well developped), specials formations... Of course it's fun playing with stereotypes, with different civ playstyles (the low on numbers but good, the zerg, etc..), but let's try to break some of them!
My intention is trying to stick to the gameplay and design applications of the discussion. Maybe it would be nice a history subforum!