I'm iffy on this, on one hand, I hate when the AI builds more then a couple of wonders (per era) in a single city and have always loved mods that put limits on it in the previous games. This time it's tricky, because not every settlement is a city and so with the share number of wonders in the game, with 10 civs across the largest map, if you limited it to 2 per city (per age), most of the wonders would never be built unless the player or the AI maps a lot of their settlements into cities. One thing that could work is allow wonders to be built in towns. Limit towns to 1 wonder each (per age) and 2 or 3 (per age) for a city.