I've got an Idea of a HUGE total conversion, based on Ancient Greek World both in Historical and Mythological point of view. Master of Olympus (or AOM) is a good example of a mix between history and mythology : a citybuilder with Gods and Creatures from greek mythology. The Impressions Games' videogame was. from 480 BCE to 320 BCE, the time is called "Classical Greece"
It would focus on several civilizations that would replace the main races of the Game : Egyptian, Greek, Etruscan, Persian, Phenician. No Roman one since Roma wasn't a big power at that time (and culturally, copied a lot from greek civ).
Basically what the mod would do :
0. Replace races by Civs i mentionned before
1. Replace Civs by City-States, randomly generated
2. Rework of World Gen to adapt to the mediterranean climate and geography. Optional : geology replacement and custom map with Anatolia, Greece, south Italy, North-East Africa, black sea and Palestine
4. Overhaul of Objects, weapons, workshops to make craft fit to that time and context.
5. Overhaul of major buildings, jobs (severe malus to mining, bonus to construction, aquifers everywhere to avoid cities of 50 z levels that doesn't fit to this context)
6. Replacing Fauna and creatures by mediterranean / creatures from greek mythology. A lot of them already exists in the game, A lot of them are to whipe from vanilla. A lot of them are to be created.
7. OPTIONAL : Graphic Set that fits well with the time period.
8. OPTIONAL : Making a good background music.
Maybe someday I'll try to build a team to develop that shit. I don't like much fantasy or SF or horror backgrounds. I'm found of History. My fav game is Europa Universalis 4, not only because of the engine / Gameplay. History FuckYea ! I loved so much games from Impressions-Games, cause even if the gameplay was bit boring, the historical background was so gooood. Buildings, objects and stuff were amaizing.