I took the Challenger/Emperor save and it did not go well. I was under the impression from a previous game or two that featured teams that the tech advantage wasn't all that big--it appears that I was incorrect. I got the GLH and the Colossus, which are both great on this map, but didn't pay enough attention to my military. I realized this early in the ADs and started to work on the problem, mostly by getting the Moai up in a city on the spoke to the SE with fish and iron, and to a lesser extent in a couple cities to the west. Too late, though. Just as I was starting to crank out units, the Shakas demanded cash and I foolishly refused. They DoW'd next turn (350 AD or so), immediately joined by the Norse. My first loss was, of course, my Moai city, and another fell soon after. I retired around 660 AD.
Try try again! In my 2nd attempt I expanded a bit faster, particularly to the west to grab stone earlier and get the Moai finished in the same eastern city as before. I also settled some cities to the south, which I hadn't done before. I didn't get the Colossus, but I did have enough units to deal with the Shakas when the inevitable DoW came again, around the same time. It was still a somewhat close thing, and I lost my westernmost city (with the stone), but I'd pulled out the few units defending it and counterattacked with a nice stack of my own a few turns later. From there on it was constant war. I'm up to around 1500 AD now and have them down to about 8 cities. The WW is killing me and they have an inconvenient island city so I'm going to take two more cities, accept peace, and then attack the Norse. I should have Mguns in about 10 turns and have had cannon and grens for quite awhile--should be enough to slug my way through their cities. The French are running quite away ahead, but I'm on good terms and they haven't followed the Steel path so I should be able to deal with them when the time comes.
Update 7/25/18: I played up to around 1700 and then dropped it to play BOTM156. I killed Charlie and have Shaka down to that one island city that I'll take when peace expires in a few turns. Zara is dead and Rags is down to 4 cities. He just got Artillery but has only built a couple and I have enough cannon and grens/rifles/Mguns that I should be able to finish him off pretty quickly now. That would put me very close to or over the Dom limit. The Napoleans are significantly ahead of me in tech but I figure that once I get infantry and/or artillery I could knock them back enough for a win, so I've declared virtual victory. Quite the slugfest, but I enjoyed the challenge (even if I failed the first time

).