I had to hack a bit into the code as the current map format doesn't seem to allow more than 10 starting positions even when directly editing the file (like we did to raise the number from 8 to 10), but I've finally managed to spawn 16 players on the Giant Earth Map.
Took me a bit of time, so I've not started to look at some code to allow the AI to move directly from Neolithic to Classical or Medieval, but I assume it should not be a problem to make it an automatic spawn (if the territory has no owner for example, or from an Empire split) with a boost in production/influence/techs etc...
Which mean we'll remove the "backup" culture (except for the human players) and left some of the AI being nomadic tribes for a few eras.
I think that I'll keep the previous versions of the map (6-8-10 players), but the choice for the number of total Empire will be "map default" (6-8-10) or between 11 to 16. Now I wonder where to put the extra starting positions for each map when using extra slots. I assume for example that using the 6 players map would mean that one want to have some free space around him.
edit: players 11 to 16 would always have the same position, what would change (or not) are slots 7-10 on the 6 player map, and slots 9-10 on the 8 players map
I also still plan to add the option to automatically spawn an outpost on the starting position to "force" some cultures to be selected. Meaning we could have a version with 10 players reserving the 10 initial cultures, and 6 extra nomadic tribes. But the Middle-East would be very crowded on such a setting (and Assyria would move to Syria)
I don't know if there should be 2 or 3 starting plots in the Americas.
Based on a comment on mod.io, I also ponder limiting future Culture choices by starting continent (as the game is already tracking that parameter), in such a setting "native American tribes" could not be picked by players starting in the "Old World".