The Incas could have a palace (A bigger bed in the middle, with walls full of gold, and a courtyard with gardens that have some statues of golden llamas and pumas, surrounded by smaller beds, with a ushnu in the middle), or temple (as a temple of pachamama, with many waters, or, more representative of the stereotype of the Incas, a small temple of the sun, like a bed with a lot of gold, higher roofs, elevated on a low platform, with perhaps a wall or circular tower or semi-circular, with water fountains, gardens with statues of llamas, corn, shrubs and peasants made of gold), that produced halberd workers (the only Inca harrier is the explorer, but it is a well-represented weapon). Instead of a temple or palace, an Acclahuasi could be added, which functions as a factory, which could produce and employ the priestesses.
Haudenossaunee could have a “Council House” that produced wise women (they were an essential part of the government of this people, which was very democratic). These wise women could be healers and, as the Haudenossaunee, like the Tupi, engineered their woods and forests, they could “build forests”. Wood is lacking in the last ages of the Iroquois, in various scenarios.
For the Lakotas, perhaps a unit could be added, I know there is a problem with representing the Crazy Horse, but the type of figure he represents, of a spiritual warrior, could be used. It could be a unit that inspired the others to have more attack, and that produced the units all on the battlefield, like a daimyo.
For the Aztecs, I think a tall temple is really missing. We have the nobles ‘hut, with that horrible name, which is a tiny temple, the nobles’ hut, which represents a Quetzacoatl-Ehecatl temple, but the great Aztec pyramidal temples are not represented. I even understand that there is no palace. Towncenter fulfills this role of perhaps home to the ruler of a small Aztec colony, but every city had a main temple, a unique building, dedicated to a tutelary deity. Could it be an ordinary Quetzacoalt temple? From Tlaloc? Tonantzin? I found it interesting that it produces Skull knights and priests, but I could have a new unit, like a Cuachic (something like Aztec berserker), that would inspire a group of units in battle. The Aztecs had beautiful and gigantic palaces, at least they could be added in the campaign scenario editor, as well as Inca palaces or temples.
They may be ideas played haphazardly, but it would add beauty and make the game more interesting and realistic.