MeteorPunch
#WINNING
Well, it's been 4 months since the first post and most of the original post is now incorrect - over time ideas have changed (for the better), and so it's practically a different game from what was presented here.
Spoilered for posterity, I guess.

Spoiler :
My initial goal for starting this mod was to focus on what I felt Civ III was best at, while eliminating all the things I don't like. Specifically, emphasizing the military game while deemphasizing Diplomatic and Space victories. Diplomatic and Space throw the game into a playstyle that is different from the rest of the game, which in itself is okay, but they make the modern era shortened into a builder race (Space), or cut it out entirely (Diplo). I would like to play a game that goes into the modern era for once and lets me actually get use of the units.
Cultural is being considered for the chopping block as well, but I'm not sure yet.
In most mods I've seen, slow expansion or anti-REX are encouraged...that's not the goal here. A standard map will be 10 Civs, and you start with 2 enhanced (1 extra move) settlers and 2 workers. Units progress in such a way that for the first era, defense is strong at the start, but weak by the end, save a few hard to come by units.The goal is for light skirmishes with barbarians alongside peaceful expansion at the beginning, but for borders to touch by the mid-Ancient Age and the possibilities of war to begin. In my test games, wars happen often and relatively early AI vs AI and of course, me vs AI.
My main goals are that it's fun, immersive, and balanced. Here are some changes and ideas in the game:
GOVERNMENTS: Governments include their own sets of buildings and units. As time goes on, more powerful governments emerge, while old ones will gain a few new advances as well. I'm trying to give each government a bit of role playing feel somewhat similar to picking a class in an RPG. New governments will generally be a improvement in power, but existing buildings may cause you to keep your current one.
Governments and their inspiration examples:
Ancient Age Governments 4000bc-500ad
TIER 0
Anarchy
Despotism
TIER I
Blood Cult (Mesoamerican)
Theocracy (Israeli)
Tribal Council (Precivilization Tribal / American Indian)
TIER II
Democracy (Greek)
Monarchy (Egyptian)
Republic (Roman)
Medieval Age 500ad-~1650ad
TIER III
Islamic Caliphate (Middle East)
Savagery (the Huns, Vikings, and Mongols)
TIER IV
Constitutional Monarchy (Euro)
Feudal Shogunate (Japan)
So for example if you switch to Feudal Shogunate, it will give you access to half a dozen buildings and up to a dozen units that are unique to this government. So in addition to normal generic units, you can use these to feel like you're playing as a feudal society...even though you may be the Zulu.
Another example, the Savagery government will give several offensive units at the start of the era at a cost to civilized society, research, and defensive ability. These are not purely "flavor" changes, as unit stats and buildings will be completely different.
more stuff
STAT FORMULAS: Units, Techs, and Buildings all have formulas to justify and scale costs.
LESS CORRUPTION: It's still there, but not as much.
CUSTOM GRAPHICS: Several custom Civ colors, Wonder Splashes, and Tech Icons.
RELIGIOUS TRAIT: All civs have this now to eliminate the annoying downtime and make government switching more viable.
BETTER WONDERS: Wonders are now almost all worth building and can be built quickly, making a less likely chance of wonder cascades.
MOVEMENT: Nearly all units have a default movement of 2 rather than 1. I think it's more fun to be able to move a Worker, then irrigate, rather than wait another turn to do so. This of course has many applications. For example, all mounted units have 3 movement points and most have Blitz.
MORE: More Units, Techs, Governments, Resources,etc. More!
CIVILOPEDIA: Probably just short, sentence-long descriptions.
Here's the Ancient Era tech tree:
Comments and criticism welcome.

In most mods I've seen, slow expansion or anti-REX are encouraged...that's not the goal here. A standard map will be 10 Civs, and you start with 2 enhanced (1 extra move) settlers and 2 workers. Units progress in such a way that for the first era, defense is strong at the start, but weak by the end, save a few hard to come by units.The goal is for light skirmishes with barbarians alongside peaceful expansion at the beginning, but for borders to touch by the mid-Ancient Age and the possibilities of war to begin. In my test games, wars happen often and relatively early AI vs AI and of course, me vs AI.
My main goals are that it's fun, immersive, and balanced. Here are some changes and ideas in the game:
GOVERNMENTS: Governments include their own sets of buildings and units. As time goes on, more powerful governments emerge, while old ones will gain a few new advances as well. I'm trying to give each government a bit of role playing feel somewhat similar to picking a class in an RPG. New governments will generally be a improvement in power, but existing buildings may cause you to keep your current one.
Governments and their inspiration examples:
Ancient Age Governments 4000bc-500ad
TIER 0
Anarchy
Despotism
TIER I
Blood Cult (Mesoamerican)
Theocracy (Israeli)
Tribal Council (Precivilization Tribal / American Indian)
TIER II
Democracy (Greek)
Monarchy (Egyptian)
Republic (Roman)
Medieval Age 500ad-~1650ad
TIER III
Islamic Caliphate (Middle East)
Savagery (the Huns, Vikings, and Mongols)
TIER IV
Constitutional Monarchy (Euro)
Feudal Shogunate (Japan)
So for example if you switch to Feudal Shogunate, it will give you access to half a dozen buildings and up to a dozen units that are unique to this government. So in addition to normal generic units, you can use these to feel like you're playing as a feudal society...even though you may be the Zulu.

Another example, the Savagery government will give several offensive units at the start of the era at a cost to civilized society, research, and defensive ability. These are not purely "flavor" changes, as unit stats and buildings will be completely different.
more stuff
STAT FORMULAS: Units, Techs, and Buildings all have formulas to justify and scale costs.
LESS CORRUPTION: It's still there, but not as much.
CUSTOM GRAPHICS: Several custom Civ colors, Wonder Splashes, and Tech Icons.
RELIGIOUS TRAIT: All civs have this now to eliminate the annoying downtime and make government switching more viable.
BETTER WONDERS: Wonders are now almost all worth building and can be built quickly, making a less likely chance of wonder cascades.
MOVEMENT: Nearly all units have a default movement of 2 rather than 1. I think it's more fun to be able to move a Worker, then irrigate, rather than wait another turn to do so. This of course has many applications. For example, all mounted units have 3 movement points and most have Blitz.
MORE: More Units, Techs, Governments, Resources,etc. More!

CIVILOPEDIA: Probably just short, sentence-long descriptions.
Here's the Ancient Era tech tree:
Comments and criticism welcome.