You can already do this. In a skirmish or random map, just set the civs of all desired players to the same one, and put them all on a team, then select Lock Teams.

UPDATE: Version 0.11.0 Added calendar (bonuses to gathering speed depending on the season and month of the year) A separate bot with support for new features has been added to the mod ( bot PETRA Expert Volatile Market) More details in the first post

Previously, I tried to make an AI player much larger, like increasing the population limit, making them build more clusters of buildings in different places to simulate an empire with multiple cities, but I could only modify the C++ files by changing a few values. I'm not even a programmer; modifying JavaScript files is beyond my capabilities.

I’m actually not very familiar with coop-mode or Archon mode, so I wasn’t referring to those. As far as I know, those modes are about multiple human players controlling a single player slot. What I’m talking about is AI-only. Several separate AI players of the same civ, each with their own economy and territory, but behaving outwardly as one large coordinated bloc — sharing the same diplomacy and roughly the same strategic stance toward other players. The idea is simply to create the feeling of a massive empire without having to make one civilization overwhelmingly strong or unbalanced.

You're talking about the coop-mode? Something like Archon mode in StarCraft 2?