On Japan: I have been thinking alot about this civ, partly due it's third UHV condition being included in your "things to work on section". I wasn't going to bring it up until your current goals
were finished but some one mentioned it so here goes.
I don't really feel that Japan as a civ in this game works at all, not just the lame first UHV condition. When I think Japan (in game terms), I think Samurai, Empire of the Rising Sun, and stereos. To reflect this i think a few changes should be made. first off, Japan should spawn later. As it stands you reach the feudal samuria period too early and then conquer china too early, etc etc. The Samurai were not used to conquer China, they were used to fight other Samurai.
At the time of the Japanese spawn, I think that the Island needs to be full of militarily strong independants or barbs. As well, I think Japan should have some kind of stability issues that go away in later times (not sure if this is possible) This could create a first UHV to unite your Island by X date, or before making contact with Europe. This would involve fighting civil wars against independants, and putting down revolts and remain stable, which would be a really unique challenge in this game, although I think this time frame should be very short to not make it get boring.
The second UHV would be to control or vassalize China, Mongolia, Kmer and allow no European settlements in southeast asia in 1950 ish. The third UHV should focus on technology. not really sure how.