With the changes to stay longer in the middle ages, the building of whaling boats has moved back. I sugest making whaling boats avilable with compass or Guilds. Whaling shouldn't be available too late, as in ancient times it was practiced. This is important for Japan and the Vikings.
Because I talking on whales already, could we move the whale in the north of Japan a 1 square to the west. This way you can put a whaling boat on it, else it can't ever be used.
Now on offshore platforms. I never understood why it needs plastics. It is so that the oil from the platforms in the North Sea is used a lot for plastics, but that's because it has a good quality. I think the building of offshore platforms should be move to combustion. It give the same recource as a well, but it needs some more investment and technology, and that's why the work boat is needed and consumed It you want it the be by a tech to show the need for more technology, then move it to industrialism. The oil will be faster available, and this meens that some civs could get some oil faster (example: Japan, with the Borneo oil)
I also allways wanted to see a reward for finishing 1 UHV. Maybe using the Heroic Epic, and renaming it to "National Monument", or something like it could do the trick. It is build in the capital and gives +2 stability (a great civ is a bit less lickly to collapse), +1 gold (a monument atracks people that spend money) and in BTS +2 espinoage point ( a great civ has less trouble finding people to spy for them).
How about being able to build cities in jungles with chemistry. Early chemsetry has early medicine, so a small colony could be build in the jungle. This could make the Dutch settle Indonesia.
Could the Statue of Liberty be a wonder that needs to be build on the coast. It was mean as a lighthouse for the Suez Canel, but it ended up in New York, on the coast. This might make it a bit easier for the USA to build it, as naval cities often produce less hamers.
If the AI cotrolles the USA when they spawn, they often become vassal to some colonial power. And that's good as the USA spawn 40 years before the histrorical date. But they often stay a vassal to long. Maybe, if they are a vassal, they should get 2 extra settles and riffleman, but only is they are vassal after 3 turn. This way thet'll ahve more cities and maybe more likely to become to big to be a vassal.
And than maybe a little bug. I had mercantilism civic and some other civ's great depression infulenced may economy. That is impossible, as a mercantilistic civ does not trade with other civs, so they can not have any influence.