I really like all these ideas (I know I haven't had a presence in a while, college is busy) I just want to play devils advocate against this way of thinking.
A lot of the people making this complaint are from AOE2, where most civs play more or less identically, even when it doesn't really make sense.
Its a double edged sword, like most design choices. Making civs follow a stricter common layout like aoe II does make trying to news and exploring easier for new players. However, after a time, all the factions just blend together into sameness and the game can loose its charm, as a lot of players are motivated by learning to play games well, and once you are there in aoe2, there is little more to hold your attention (which is why the latest AOE2 dlc factions have been straining those common layouts as much as the devs dare without annoying their famously fastidious fans)
The counter side, like AOE4, AOE3, or AOM; Makes civs that differ more from each other can make it harder for newer players to expand and learn the various factions, because different factions play differently. However, it can keep players on their toes as they play, as the differences in different factions can ellicit different responses from the player depending on the matchup. It can also keep older players engaged, since it takes longer to master each faction.
I know it was a little tangent for this thread, but since the thought came up I felt like here would be a good place to mention it. I think the women and helot dynamic was a very interesting design choice, like others in this thread.
I mostly just wanted to say that we shouldn't be afraid of making each faction unique, especially if it expands the historical basis of this game, which it prides itself on