= Mods that replace individual factions =

No, just so that any city can be placed in the location of any other.
The idea is this: the map can have a maximum of 8 different factions, but if the above idea is feasible, then these can be any (up to cities from mods).
The map would be created very simply: the necessary mods would be placed in a folder, and then a map would be created through GSC or an editor, like any other, but most likely a special editor will be needed that works with mods.
We cannot directly add new factions, but we can create the illusion of adding them.