...I'll bet your tech tree is interesting.
Its based on RaR v1.04beta
I've tweaked it by switching alphabet with writing; all civilizations developed some form of writing. The major advance was invention of alphabet. Historically the benefit of alphabet is that it facilitates the diplomatic corps (and everything associated) and encouraged research. A language written with 26 letters is so much easier to learn than crazy Chinese / Japanese writing where there's a character for each word in the language.
Secondly, I constrained the appearance of various resources based on 'knowing' the resource and other relevent technologies. For example, horses are known by Mongols initially. They're the only civ that see them initially. Once the Mongols develop the other necessary techs, they can build units requiring horses. Once you know horses, they show up and they can be eaten. After a while its discovered there's more to these things than steaks.
I've done this with tobacco, corn, potatoes, rice, tea, etc.
The thing I discovered is that CivIII is extremely weak with regards to production of food related to tech.
Corn is discovered by the Euro's in the America's. Potatoes are known initially only by the Inca. The incorporation of either into Euro diet was the predominant reason for the subsequent population explosion; something that otherwise would be absolutely impossible if depending exclusively on existing wheat, barley, mutton, turnips, gruel and sticks and twigs in the lean years. Can you imaging living on nettle soup like these people did? Unbelievable.
I've replaced saltpeter with sulphur. Saltpeter can be made with countless process. Easy enough after discovery of alchemy (it so easy its pointless to make it a resource constraint). The truly critical resource for gunpowder is sulphur. Technically carbon is also a requirement, but how to make that a resource? That was one of the big driving forces behind the coke furnace, i.e., bituminous fuel; the Britons were running out of trees.
Oh, yeah, I added oil seeps and placer coal for the ancient era.
I did away with the Franks and put the Celts into their most plausible original start position. I did away with Carthaginians and created Phoenicians. I added Mayans, Sumeria, Hattusa, Navajo, Abyssiania, Siam, and Sioux. And then sprinkled the globe with historically accurate minor tribes.
I made alphabet highly unlikely for MesoAmerica to research. Human sacrifice exists for the various historically accurate civs, e.g., Celts.
Oh, and one minor thing: any unit built reduces population by 1. That definitely was an issue historically, i.e., warriors weren't there to work the fields. If you want an army you better figure out how to feed it. But I ameliorated that with techs that incresae population 50%, e.g., corn, potatoes.
But ALL terrain causes anywhere from 7% to 25% disease with median of 10% (done away with by Sanitation) + periodic plagues (begin 1650 BC variance 500, duration 1, 80% carnage, grace pd 1, max occurance 100). The jungle does the 25% damage - yellow fever / malaria was some nasty crap for a LONG time - and mountains 7%.
The other tweaks: game starts 9000 BC w/ zero treasury balance and no techs (except mining and knowing own culture). 700 turns gets one to about 2000 AD and the subsequent 300 turns to about 2100. The resolution unit for turns is 'month'. The final 300 turns are 3 mo. @ eaches. Civ advances should be coming pretty hot & heavy by then.
Also, the 'knowing' techs can't be researched (but can be traded). That means until any civ has contact with another civ possessing any arbitrary 'knowing' tech, well, then they're just not going to know 'bout any of that will they?
All this played on Teturkhan's 362^2 map with his original resource placement + integration of RaR resources & import of RaR rules into that.
Other than that its all pretty much basic original CivIII.
Much to my chagrin, playing CivIII for the last few years has amounted to firing up the editor and tweaking the map, the rules and the units (both required techs and civ unique and upgrading animations where available), leaderheads. Oh, and maintaining the spreadsheet.