All that would be needed is to password protect each civilization in multi setup. The save could then be passed around. As one gets the save they put it where it belongs and then open their civilization in the Load Game.This extra step would only be needed if it is a multi player game.

People are smarter than any AI at the moment.

The person who makes the game could assign a pass to each civ as it is made in multi. Then all the player has to do after opening is select their Civ, enter their pass, play, save, send.

The last person in the game would be the one to process all turns if not done by each individually on "Turn"

Unfortunately I am in a very small minority leading me to think that I have to hope for something in an expansion pack.

No; I do not want to give up on a feature that would make this game last for a long time for me.

If I can just get enough to make it barely work I can make a PBEM howto guide.

I could have done it in SOTSII if the empires could have been password protected.