Historically, mesoamerican civs did not use crossbow. Instead they only use bows and flatbows to fight.
I propose the mesoamerican archer line should be archer -> flatbowman -> Master Flatbowman instead of crossbowman and arbalest. Meanwhile, they have the same stats. While the monks can have different appearance as well as Xolotl warrior/knight, why not the archer-line? Any thought?
The unity of unit visuals has one simple reason except laziness (:P) to keep clear overview on the battle fields. If every civ or every region has their own skin of generic unit lines it could become confusing if you have 8 armies fighting in one spot. But reskining your pov is always possible and you have to bear the consequences. And there are reskinning mods
Xolotl is no normal unit, that even when accessible is useless to produce and monks still look like monks. Even Imams are not in the game just because they look so differently. But people would need to learn different between three archer types just for three civs. And you can always say whatabout, it wont happen, for good reasons. You can make it urself if you wish it so much.
I just can repeat myself over and over again: this is a PC-game, not an historical accurate encyclopedia. Change things like that would be just confusing for players, who are used to this game for 10+ years (suddenly other appearance of the units) and a waste of time; time which could be used for more important things (e.g.: fixing the drops in multiplayer).
I don’t want to be rude by the way: I understand your point, and maybe, if you are more interested in historical things than I am, little details like that bothers you. I just think that the disadvantages predominates the advantages.