If I would add anything I would increase the new world.
Maybe add North America with the Natives that live there.

But then if I could I would make an entire option to travel to the new world. (new map, but still a bit the same campaign, you're ale to travel to the new world and back to the old world), take in mind that by the time you can travel to the new world you will have loads of Europe.
You can then take loads of America: entire Caribean, Mexico and a big part of North America. But this might be better for an expansion, then adding this in this game, things might get too big.