Nobody asked, and I don't want to sound (uhm, read?) like a jerk, but these "diety" challenge games where you give yourself beyond diety advantages are a little silly. I can see how they would be fun (like when playing for your first time at settler and bulldozing everyone around you), but they are less difficult than a normal prince game. Used to see this a lot in Civ III games too. People would set up "impossible" Sid scenario games, but give themselves four grassland river cows, iron, horses, and three luxuries, while everyone else starts in miles of jungle...
If you played this again, maybe you could play on a pangaea map and have one marine per opponent. Start them out at home, so they have to walk to their various destinations. And let the civs trade tech. Instead of a starting with a priest or a merchant, couldn't you just start with a set amount of gold to be used only for research? Enough to get to break even 100% tech in say 150 turns/however soon you can build a market? Or maybe not allow yourselves to build The Great Wall. That would force you to keep at least ONE marine at home...
I think this could be a fun varient, but it seems clear that freightening the AI from settling a second city for an extended period, or even meeting/trading with neighbors takes 99% of the challenge out this. I hope that your next OCC venture at least finds the parking lot of the ballpark of a potential loss. Good luck in any event.