I had an idea for 2021's balance of power, but with a starting time circa 1300 - 1400. On the GEM.
I researched and recorded population, land area, major cities, military strength and composition, GDP, and GDP per capita for all 50 civs for the scenario. I then applied this info holistically rather than literally. For example, tech serves as a viable substitute for GDP per capita, etc..
It's been playing amazing so far, though I don't understand everything about the gamespeed and era xml's. For example, the WB XML says "ancient," because I was afraid to change it. HOW IF AT ALL DOES THIS AFFECT GAMEPLAY? When I play the different civs, they start as the era their tech dictates - ranging from Ancient to Rennaissance - but is there also a "master era" for the game, as the WB XML seems to imply? I fiddled a lot with research modifers, etc., without really understanding what I was doing, and without knowing how to save original files. All I know is that the scenario SEEMS to play fine now.
I settled on 1367 as a reasonable start year. I've played many games through 100-200 turns so far. Most civs are immediately vassaled by China, Russia, France, India, etc, especially China, who always has about a dozen vassals and has gone as high as twenty. Japan is also very strong, but isolated, and Germany has a wide range of outcomes. I may have made England a bit too weak, but hey, it's 2021, not 1871. America begins as, I think, the only civ with Rennaissance tech. Generally, but not strictly, there are three tiers of civs: masters, vassals, and independents. Italy seems to be the most representative example of an independent-tier civ. Other civs seem to be independent due to geography (or maybe leader traits) rather than power.
Anyway, I'm deep into an Indonesian game right now. I don't expect to win, but it's very fun, so I hope to play it through to the end of the game to see how the scenario develops.
Speaking of gamespeed, I accidentally modified the original XML, so that it says "Normal," but it's actually more like a chimerical monster of marathon, epic, my own thing, and possibly also normal. Kind of a mess... but as long as the scenario is fun for now, I won't stress about not having the original XML's.