Since suggestions and such are allowed, I thought I would throw my hat into the ring with two suggestions, though neither are important enough to need an update before the PB/PBEM or anything, but is more food for thought. Specifically, I propose that Ethiopia/Japan's UBs should be buffed/replaced and here's why. (Since you said you don't want small changes, it'd probably be a replacement)
Ethiopia: The problem with Ethiopia is, right now, it feels like a strictly worse version of the Ottoman Empire. Janissary are generally going to be a lot better than Oromo Warriors, save on defense: I'll take +25% vs. Archery, Melee AND Mounted compared to the 2-3 First Strikes. However, the Ottomans also have the awesome Hammam unique building, while Ethiopia has the near worthless Stele building (Even in cultural victories it isn't amazing and culture is hard to do in MP). In addition, the Ottomans have Agriculture + The Wheel, which is most likely preferred to Hunting + Mining in a lot of situations. While Ethiopia doesn't need a huge buff, it would be good if they had a good unique building that made them a reasonable option compared to the Ottomans.
Japan: Japan has a UU and techs that, while they would not be top tier, would at least make them pickable, but the Shale Plant is one of the worst UBs in the game, both in terms of power and design. Replacing it with something that doesn't suck would make Japan viable...or at least buff it some so it isn't just +10% Production tacked onto a Coal Plant, which is incredibly weak at that point in time. Maybe double speed for Productive leaders or an additional building boost? Not as important as the Ethiopia one IMO, but Japan has a lot of room for a useful and flavorful UB that would essentially let another civ be viable and I dislike the Shale Plant a lot.
Ethiopia: The problem with Ethiopia is, right now, it feels like a strictly worse version of the Ottoman Empire. Janissary are generally going to be a lot better than Oromo Warriors, save on defense: I'll take +25% vs. Archery, Melee AND Mounted compared to the 2-3 First Strikes. However, the Ottomans also have the awesome Hammam unique building, while Ethiopia has the near worthless Stele building (Even in cultural victories it isn't amazing and culture is hard to do in MP). In addition, the Ottomans have Agriculture + The Wheel, which is most likely preferred to Hunting + Mining in a lot of situations. While Ethiopia doesn't need a huge buff, it would be good if they had a good unique building that made them a reasonable option compared to the Ottomans.
Japan: Japan has a UU and techs that, while they would not be top tier, would at least make them pickable, but the Shale Plant is one of the worst UBs in the game, both in terms of power and design. Replacing it with something that doesn't suck would make Japan viable...or at least buff it some so it isn't just +10% Production tacked onto a Coal Plant, which is incredibly weak at that point in time. Maybe double speed for Productive leaders or an additional building boost? Not as important as the Ethiopia one IMO, but Japan has a lot of room for a useful and flavorful UB that would essentially let another civ be viable and I dislike the Shale Plant a lot.