I have not had a chance yet to play C2C. I do not have anything wrong with designing cultures how you want and going ahistorical, but to get the beginning culture we want to alter it is in need historical flavor in the early periods. There would need something to distinguish the regions.
I really do not want a silly Mesoamerican swordsman. I would rather have a staff with serrated stone edges. I rather see uniqueness that did exist. Not technologies dictating a metal age from the old world.
I would rather see advanced Mongolian horse tactics that are only available to similar cultures who lived, sleep, and ate (even made jerky by riding the horse) on a back of a horse. This is not a tech that should be available to Romans.
I am not looking to iron out culture so much in the tech tree, but more or less not just playing the same line up of UU, UB, and some leader with traits. I would like extra techs to make unique abilities. I just want something more interesting than the default game.
If you have a large assortment of changes, I will see it when I get the chance to play the game. So Hydro you are right. Before I can really say much more I need to try C2C. I am not thinking of defining culture so much through techs although you could. I am more thinking when I read about civilizations in mods how lifeless they seem to me.
Edit: I mean I would like the known in and "what if's" from interesting knowns. For example some early metallurgy was done in the Americas, but never a scale like Old World. Just making a bunch of metal weapons in the Americas is a "what if".
Well considering that no everyone plays on an Earth map, civs are bound to be in places hey historically were not similar to where they were on Earth. In a random roll of the dice we could have England with Llamas, Silk and Obsidian, while China has Camels, Pumpkins and Silver and the Aztecs with Elephants, Wheat and Iron. How would those societies develop?
Without making atl-timeline cultures I have tried to make cultures that fit different niches. For instance before Europeans brought horses to America there were no horse cultures. But if there had been then they most likely would have been like the Cheyenne or Comanche.
Likewise the what ifs of other mixing cultures. What if South America and Africa met early on? Or North America and Australia? What kind of mixed culture would come out of them? These are the kinds of questions I would like C2C to try to answer through gameplay.
You can assimilate other nations and make them into your own. Thus the game really evolves by what geography is round, who you meet, what happened in your game and what choices you the player has made.
I would love to have special bonuses available, however I would not like them to be preset to a specific culture. Or if it was it would be to the culture resource and not the civ you picked.
Such as your Mongolian horse tactics could be a special promotion and building you can make if you have Mongolian culture. But should not be something only get by choosing the Mongolian civ at the beginning of the game.
However a better way would be to apply such things to the
Cultural Heritage mod. Where if you did the right set of requirements you could get that cultural perk to your overall civ. Thus allowing the player to shape the culture of is own civ rather than a predefined path of "oh i picked Mongolian so I get this this and this. because Mongolians did that historically."
Having more dynamic choices means overall a lot more variety. Never having the same game twice or encountering the same civ twice.
Also you should really play C2C before you try to mod it. I can talk about it until I am blue in the face but if you have never played the mod you just will not understand.