I’d recommend after the teams form that they all agree to play one difficulty only. - IMM or Deity.
That makes sense, so let me pitch Deity by addressing some of the usual criticisms of that level.
In a normal game, the biggest advantage the Deity AI has IMO, is the start. They get extra settler and workers which means they don't have to spend 12-15 turns building a worker. That jump start means they grab land and virtually all the early wonders. Well, none of that is a problem in this scenario. We've been given some land and we're already surrounded...even if you play at EMP.
Deity AI techs fast. Yes, but we've been given a ton of advanced tech. We could even trade that tech if the AI was not given those same freebies, so having the AI tech fast makes the game
easier to finish faster. They do drive a bit harder bargain on those tech trades, but that's fair since they're already being stupid enough to trade the human tech as it is.
Cities grow faster, workers improve faster. Again, all things that can boost your speed.
It's not like the AI is more aggressive at Deity. Or smarter. Or harder to Please (Diplo.) The only 'scary' thing left that I can think of is their production goes from 80% cost down to 60%. So something that costs 80 on EMP would be 60 hammers. Doesn't sound like a big deal to me...some might disagree, but remember, Deity AI's don't build more units. They'll still defend a city with 2 units. I think this minor boost in their production gives them a small fighting chance...instead of getting steamrolled as usual.
And again, similar to having the AI help you tech faster, they will also build you free forges, granaries, courthouses, etc.
Seems like sossos
did intend to create a Deity game and make it approachable by players of all skilled levels.