Here's my Armchair Imagineering for my conceptually favorite park: bring a new attraction to each country.
In Mexico: A live swashbuckling adventure show featuring a Zorro-like character taking down a baddie in the Mexican village. A real Errol Flynn type thing with people swinging from chandeliers and curtains.
In Norway: Already changing.
In China: Put in a Panda Preserve. In our popular consciousness, pandas are very much associated with China (in fact, the Chinese govt. owns all pandas in the world. In order to exhibit a panda, you have to pay royalties to the Communist Party every year. There's your knowledge drop for the day). Imagine going through a pagoda out front and then emerging in the back into a lush Chinese rainforest, complete with a waterfall, with 'local workers' protecting the pandas from poachers. Pandas are conspicuously absent from AK.
In Germany: Give me a good, next-gen dark ride based on the fairy tales and legends associated with the Black Forest. The Black Forest is even today important to the German spirit, and many of the fairy tales Disney uses can be traced back to Germanic roots. But don't make it 'friendship is magic' like the MK. Give it a little bit of a darker bend, like late '90s Tim Burton.
In Italy: I'll take a nice Omni-mover people eater with some good old fashioned animatronics giving us a crash course in the Roman Empire, but with that tongue-in-cheek style that you might have seen in World of Motion. Going from room-to-room following a person as he gets up to hijinks in the market, the senate, etc.
USA: Hehehe. If I could make one single change, it would be to gut the American Adventure show and start from scratch. Its view of US history may have been ok for the '60s, but our understanding of our own story has changed drastically since EPCOT open. That show is so filled with half-truths presented as fact (example: there was NO SNOW at Valley Forge in reality, but not according the show!) and really only tells the "American Adventure" from the white perspective. Get a diverse team together to re-write it. Keep Ben Franklin and Mark Twain, keep it as an animatronic show, but add a third narrator and some new scenes. And get a team together that can help round out our story so that it is more truly American.
Japan: I would love to resurrect the Godzilla roller coaster. I would also settle for an expanded Japanese garden, especially if there was a portion indoors that was "always night" like the Mexico pavilion. Imagine that! Beautiful paper lanterns coloring the babbling streams and koi ponds.
Morocco: Look up "Fortress Explorations" at Tokyo DisneySea. Do something like that, but set in a fortress in Morocco with appropriate rooms. Add a scavenger hunt/quest component so it becomes Tom Sawyer's Island meets Wilderness Explorers. That pavilion is all about exploring the nooks and cranies. This would plus size that immensely.
In France:
In UK: The least possible, but get that Lord of the Rings license and build a Mines of Moria adventure. The Dwarves come to get Bilbo and head out on a new quest. They run into a few 'old friends' and come up against the Balrog before escaping.
In Canada: Do an attraction based on the legends of the Northern Lights told by the Inuit populations in the north.
If I had a gazillion dollars, that's what I would do! I love EPCOT so much. Every attraction that currently exists there I really do like. Spaceship Earth is still my favorite in all WDW. It makes me sad that it gets so neglected.