I really like that we are able to discuss like this about all these future UCs, but I think we need first and foremost to be sure that everything already done works well. This is why I think we should not speak of civs not in the
UC by Civilization until we are happy with what we've got
Lol, I prefer to have all civs partially planned before we engage in the coding because it helps us identify "holes", and techs/UCs which are over-stacked. With the work I've put into the 4UC by civs spreadsheet, there are only 4 civs still laying fallow since your original thread: Huns, Zulu, and Persia.
re: the Inca tech spread, here's where they're at right now
1 Ancient UU (Slinger)
1 classical UI (Terrace farm)
There's so much material to pick from for Incan architecture and culture. Seriously, this culture is one of the most fertile and distinct civs in the entire game
Here are the proposals, with a brief description of what that UC is in real life:
Ancient/Classical UU (Pathfinder/Scout - Chasqui) - The messengers, essentially a "pony express" made of marathoners instead of horsemen. They were very fit and well-trained. They could read the Khipu system, and had relay stations which housed fresh runners called Tambo to make messages travel quickly.
Ancient UB (Granary - Qullqa) - storehouses for basically everything, not just agricultural products. The Inca had a central command economy at very high altitudes, so they were very vulnerable to food shortages. The Qullqa stored potatoes, building materials, feathers, luxuries, tributes. Royal Qullqas housed the entire coca production of the Inca empire, which held a monopoly on coca, and distributed it to chieftains, nobility and for diplomatic purposes
Ancient/Classical/medieval UB (Caravansary/Customs House/Barracks - Tambo) - Relay station, Inn, Barracks, Administrative compound all rolled into one. They kept Chasquis ready to run messages, but also housed imperial garrisons and controlled the local Qullqas
Classical UB (Library - Yachaywasi) - Centre of learning within the Inca Empire. They taught customs, mythology, combat, and how to read the 'khipu', a system of knots on strings which were kept for administration. The khipu system was the closest thing the Inca had to a written language.
Classical UB (Aqueduct - Chicheria) - Breweries/Speakeasies for the production and sale of Chicha, a traditional corn beer. This drink had religious/ceremonial uses, but also was a part of everyday life of the peasantry, who would drink chicha during festivals. As a personal note, chicha tastes awful; the stuff is just rancid.
Medieval UB (Castle - Cyclopean Citadel) - The Inca rarely relied on fortified structures and sieges in their warfare, but the fortifications which do exist are truly impressive. Inca masonry would use massive stones, sometimes weighing as much as 4 tons, and cut them to fit like puzzle-pieces against each other - a technique which circumvented the need for mortar.
My thoughts:
Chasqui should be a scout, or else Inca is doubled up on ancient era units, and having two ultra-early UUs would suck because you don't get to build many of either. I don't think they should be able to build roads, since they were runners, they didn't actually help build them.
The presence of a UI, I think, gives some liberty for where the UB should land. I don't think it much matters, but avoiding the classical era would be a plus. My personal vote would be towards either the Granary, Caravansary or aqueduct replacements (we haven't done any of those buildings yet).
The Aymara mod has a Coca resource which we could use. Adding new resources, as others have pointed out, is a pain in the ass, but having a building which gives cities a copy of a unique luxury could give players an actual reason to attack the Inca. Right now the Inca end up being ignored, because they are incredibly hard to invade, and there's frankly little incentive to do so anyways. Since Coca (the natural source of cocaine) is a pain and appetite suppressant, it was given to workers to make them work harder. You could make the monopoly increase improvement rate, which would be a unique monopoly attribute.