What makes a scenario is more its mechanics than just its setting. Anyone can say "let's set this in ancient Mesoamerica" but how that actually translates to interesting gameplay is the important part.
I thought the introduction of Ideologies meant an overarching 20th century scenario was all but certain, especially with how it worked into Tourism and the new culture victory. Something revolving around America, the Soviet Union, and Nazi Germany being the major powers that start with high Culture and Tourism and their Ideologies quickly growing into place, while lesser nations and even city-states choosing them for their own. Likely it'd be set up so Germany would be surrounded by an incoming swarm of nations taking Order and Freedom while they're stuck with Autocracy, so they're left with little other choice but to go crazy conquest, but the ultimate aim of the scenario is not world domination but rather a culture victory, or even forcing every other nation on the map to change to yours. Probably the Tenets would be subtly changed in some ways- the scenario would start off with Germany broken down from WWI, but Autocracy would be adjusted so they can rapidly get on their feet and storm their way to being competitive with the other powers on the map.
The American Revolution is something I'd wish more would be a part of a revamped Conquest of the New World, where, once you establish your colonial empire as a European, various forms of dissent grow and it becomes harder and harder to maintain territory overseas, especially as they grow in their own local power. This becomes especially true if you have swathes of land conquered from the natives, as, if you're playing as them, you don't entirely lose control of your cities should you be taken over, but instead instigate actions among your conquered people, and when your lands are vanquished, you lead a revolution to form a new independent nation with the spirit of the old fashioned from new knowledge. Or, if entirely European, at some point your founded cities start rebelling and growing in unhappiness, and at a certain tipping point, you have an option to functionally jump ships - either continue playing as the European nation, or take on the role of rebels seeking to overthrow the tyranny they see with your empire. Points are ascribed for rebel nations, and they can prospectively sweep their way up the charts faster than the Europeans, getting massive amounts of points for reconquering cities that the player had just founded. Obviously this would need balancing, otherwise people would game the system to intentionally make themselves weak and then jump unto the rebels to win the game, and it'd probably work simply by having dissent grow faster as cities become more fortified, militarized, and industrialized, so the rebels must fight the bigger opponent regardless of previous actions, or not form at all if your colonies just stay kind of small and mellow.
