The Mexicas (better known as Aztecs) were a particularly warlike Nahua people, however they had more things to admire than just that.
Their society was very communitarian, people were grouped in Calpulli that resembled clans or noble houses, but could be formed by sharing the same profession as a guild or by having a common tribal god. After the reforms of Tlacaelel everyone could access the nobility for their merits (usually military) and being born the son of a nobleman did not necessarily make you a noble, also with this they began to consider themselves the chosen ones of the sun and war. Education was public and compulsory, the children of commoners were boarded in the Tepochcalli and those of the nobles in the Calmecac and although they studied with teachers and subjects at different levels, both were taught to fight, endure pain and precariousness.
In war they were specialists, they used their merchants as spies and they had a system of ranks in addition to military orders that could be accessed according to the prisoners captured in battle, these prisoners were later sacrificed and their skulls used to be put on the wall of skulls or a tower of skulls. Being in a military order was a symbol of great prestige and generals usually comes from these.
They used obsidian to make tools, weapons, and even medical implements with knives for surgery. They grew in Chinampas, farm plots that floated on Lake Texcoco, did not need to be irrigated and were extremely fertile.
- Military buildings work 15% faster.
- Melee and range infantry move 15% faster.
- Relics and sacred sites produce 35% more gold.
- Military units deals 100% more damage against buildings. (Don´t have siege units exept rams)
- Houses can garrison villagers and shoot up to two arrows.
- Traders have the same line of sight as explorers.
-House Of The Darts: Can recruit units of the warrior societies and acts as an outpost shooting arrows.
-Tzompantli Tower (Tower of skulls): religious structure that increases the speed of nearby units, they can also garrison a relic such as temples, only in this case, in addition to generating gold, it increases the damage of nearby units and buildings.
UNIQUE UNITS (House Of The Darts Units)
-Jaguar Warrior: Replaces the man-at-arms and deals more damage. Can enter in stealth mode.
-Eagle Warrior: Shoots a javelin every 8 seconds, in melee have a small anti cavalry bonus. Is a fast runner troop. Can enter in stealth mode.
-Cuahchic: Elite melee unit effective against armored units.
-War Priest (From the temple): Replaces the monk, is a melee infantry unit but have all priest abilities
AMERICAN CIVS UNITS
This aren´t unique units, but only are shared with other civs like Incas and other possibilities like Mayans and Tarasco/Purepecha.
-Slinger: Fast shoot and move unit, but don´t deals much damage.
-Javelin Thrower: Replaces the crossbowmen and have bonus damage against ranged units.
-Canoe: Cheap, fast and weak archer ship.
To age II
Tlatelolco Market: Acts as a market with better exchange prices, in addition produces 15% more gold from the merchants.
Tepochcalli: Trains spearmen and slingers at twice speed, also research their upgrades with 50% discount.
To Age III
Calmecac: Is similar to the tepochcalli, but for nobles. Train jaguar warriors, eagle warriors and Cuachic free, but four times slower and only one of the options at time.
Temple Of Quetzalcoatl: Can garrison one relic as a temple and boost the production of the nearby buildings, the relic produces 20% more gold.
To Age IV
Huey Tlatoani Palace: Is a stronger version of a fortress, also produces gold.
Ball Game Court: Units of the hose of the darts gains 20% more hit points, the nearby house of the darts shoots an additional arrow.
- Tlacaelel Reforms: Units of the house of the darts are 15% cheaper.
- Floral Wars: Infantry melee units gains +3 of damage.
- Atlatl: Javelins +2 of damage and +1 range.
- Chimalli: Archers gains a shield; this provides +1 pierce armor.
- Temazcal: Buildings gains a fast-healing speed for garrisoned units.
- Umbrella Shield: Spearmen gains +1 pierce armor.
- Chinampa: Farmers works 50% faster.
- Obsidian Surgery: War Priest +20% of healing speed.
- Universal Education: The rest of the technologies cost -15%.
- Calpulli: Villagers can be trained in pairs.
Not only Tenochtitlan, but most of the Nahua cities shared a very similar architectural style, with pyramidal vaults on the roofs of many structures or conical points in the chapels of some pyramids.
The houses used to be painted with multiple colors and geometric motifs, the streets and bridges of Tenochtitlan were made of white lime and the lake capital could be traveled by canoe in many of its neighborhoods.
Well, try to balance the lack of gunpowder and siege units with elite soldiers and swarming capabilities to overwhelm the enemy. For the water i can´t do too much.
Another idea from the Calpulli tech, is change it for a civ bonus (or also tech) that makes the houses have an aura with which they improve the speed of collecting resources by 2% or 3% each one, it could accumulate up to a maximum of 30% in this way, but in any case the aura would not be very big.