I have a full power/mythic beings outline for each of them, but it will take a wall of text and most people won’t read it, so here is just an overview. 
That is a pretty big list
Ideas for Aztecs
Aztec starts with more villagers and no scout units
Villagers can be upgraded into hunters
Villagers are stronger then in other civs, deal more dmg and attacks faster
Hunter are infantry unit but with 20% move speed increase and range attack
TC for Aztec is pyramid, have low cost and can be build in big numbers but they still have house-like smaller pyramid building that boost villager training speed and can be build only connected to main pyramid(up to 6 for each big pyramid?)
TC can train villagers and priests
Villagers garrison TC after they was produced.
More villagers you have less they will cost. (50% reduction max?)
Priests passively produce favor, but slow.
Temple can contain up to 4 priests (1 for each age)
Temple connected to TC
Aztecs gain favor by doing rituals in temple. For ritual player use villager as recourse. For each Priest player will gain more favor from ritual.
Gathering are the same. Cost gold and wood.
Aztec spread between 4 aspects(Main gods): The Serpent, The Jaguar, The Eagle, The Coyote.
The Serpent (Quertzalcoatl) – production and trade
The Jaguar (Tezcatlipoca)– Military buildings
The Eagle (Huitzilopochtli)– TC, houses
The Coyote (Citlalicue)– Temple and mythology
Aztecs have 4 main military buildings associated with 4 aspects: Earth, Stars, Sun, Rain.
Villagers inside TC are used as resource for production of military units.
Earth(vs buildings) – Age 2 - Warrior with shield and club, Age 3 – Warrior with Shield and bolas(+vs arch)
Stars(vs cav) – Age 2 - Warrior with tepoztopilli(spear), Age 3 – Warrior with Spear-trower(+vs buildings)
Sun(vs inf) – Age 2 - Warrior with 2 axes, Age 3 – Warrior with 2h Macuahuitl(+vs cav)
Rain(vs arch) – Age 2 - Warrior with blowpipe, Age 3 – Warrior with big bow(+vs inf)
Aztecs doesn’t have any cavalry but their infantry units 5% faster for each Age(+20% in Age 4).
To create heroes player must send 2 unit of the same type into the Temple and after certain time one of them will die and another will became a hero(30% stronger then Atlantians heroes?).
Aztec can build Towers only as part on the walls.
Towers deal less dmg but have poison and attack faster if more units are inside.
Mythical creatures
T2 – Chaneque, Tzitzimitl, Ahuizotl, The Atotolin
T3 – Cipactli, Teuzauhtototl, The Quinametzin, Amoxoaque
T4 – Managua, Cueyatl, Xochitonal,
The difficulty with Mayan/Aztec faction are the myth units, there really aren’t a lot of mythological creatures to choose from, not as much as the other cultures, Egyptians have the same problem to be honest, but at least you can make up myth units for all the gods.
I think Cipactli and Tzitzmiltl should be T4 myth units.
Only one minor god per age?
Gods being swapped around hapened before release, when things like that could be expected.
Now, that we’re after release, I don’t think it’ll happen without a very good reason.
