This is what I would do:
Magic Kingdom area:
1. More sit down restaurants. Maybe another proper Italian restaurant, something that doesn't have to be super themed.
2. Indiana Jones in Adventureland. You could walk through the Jungle Cruise(over bridges and along walkways) to go into an underground temple(where the whole ride is actually underground, so views from outside the park arent ruined), it would be a similar ride to that at Disneyland, maybe with a new storyline.
3. Elongate the Seven Dwarfs Mine Train - it's way too short. It currently has two sections to it, before and after the mine, I would add an underground section in the mine. You currently enter the mine before turning left and then up the lift hill, I would change it so you go right, see the same mining operation mirrored from before, before going down again instead of up a lift hill, you would go past glowing gems while you go through this section, before meeting up with an elongated second lift hill, where you could go into the same final outdoor section. The exterior would stay exactly the same, everything new would be below everyone's feet.
4. Replace the Tomorrow Speedway. It would need to be replaced with something all electric, fast paced and exciting, yet still stay retro - so a Tron ride wouldn't work here, it's too modern futuristic, and Space Mountain is already there as a dark ride roller coaster, and it would need to be transport based(probably) or have some real connection to a retro future, maybe something like Rocket Rods(but actually good). Or the submarine voyage returning, that would work well.
5. Fix Tomorrowland Transit Authority Peoplemover. It keeps breaking down, and I really enjoy it.
6. I would create a new land behind fantasy land. I have no idea what the theme would be - include a roller coaster, a dark ride, and something else.
7. A new luxury hotel between the Transportation and Ticket Office and the Contemporary, which could connect with Monorail.
8. Remake Pirates of the Caribbean with better tech and an actually storyline(I still enjoy it now, it could just use an upgrade).
Epcot:
Epcot needs to both stand by its original ideologies, and appeal to visitors - so it still has to be about the world and the future, but it needs to have a range of rides to bring people in, ones which are related to its ideologies. I think it shouldn't have too many references to films in terms of its attractions, as thats what the other parks have, I wouldn't enjoy epcot if it were full of film related rides(a few is fine), as it would defeat the point of Epcot.
1. Test Track, Mission Space, The Land and The Seas are all great at the moment, maybe clean everything up, make everything still look quite retro futuristic, but with some modernity(small touches, like large floor to ceiling windows). I would keep all the building in the middle of future world, just clean them up.
2. Ellen's Energy Adventure would have to go, maybe replaced by a fast paced time travelling ride(indoor), as I could see something like that fitting in well. Some people have said a Guardians of the Galaxy ride, but(even if Disney had the rights to use that in Orlando) that wouldn't fit in at Epcot, it would fit in, however, at Hollywood Studios.
3. The Imagination pavillion should keep the building, but build a ride based on Inside Out, which explores the senses and the mind, but might have some sort of twist.
4. Innoventions should be moved to the old Wonders of Life pavillion, and updated dramatically, so that it is a fairly major pavillion. I would also add a large new building out the back of the new Innoventions building, which would house a lab where innovation would actually be taking place(like improving efficiency of renewable energy production, something that can be applied to the real world, and is applied to the real world), this could have a ride touring it and showing latest innovations.
5. I would add an attraction inside the old Innoventions building, it would be a dark ride with a theme that I can't think of, maybe an omnimover ride.
6. Spaceship Earth should be renovated, but the ride shoukd stay about the same, the same scenes with improved animatronics, a more reliable omnimover system, etc. It still has to look right, so not too high tech or anything, very similar to what it is now.
7. The World Showcase needs improving as well. Trackless ratatouille ride in France, Soarin' over the UK, a Japanese ride that is relevant to their culture(maybe a dark ride storytelling ancient Japanese legends or myths that could put you in the middle of the action - same with China), and an attraction at every pavillion, however small. A Switzerland pavillion could be created with a recreation of the Matterhorn bobsleds at Disneyland, try not change it that much from the Disneyland version - hopefully this wouldn't scar the view from future would, or from other pavillions.
8. The Odyssey restaurant should be renovated and made a really high tech, modern restaurant serving both quite normal, and futuristic food and drink(sit-down).
As much as I'd enjoy a Tron coaster, I don't think it would fit in the retro futuristic style of Tomorrowland or Future World in Epcot(as Test Track is already great). It could go alongside Test Track maybe, launch, loop around the test track building, before going inside in a building behind Test Track. It could, however, go nicely in Hollywood Studios.
Hollywood Studios:
1. A Tron coaster, which would fit in well with the park, as it also wouldn't fit in in Tomorrowland or Future World.
2. Bring back the Car stunt show and tram tour.
3. Radiator Spring Racers and Cars Land.
4. Various dark rides should be built.
Animal Kingdom:
1. Animal Kingdom is fairly perfect now that it has Avatar - lots of thrill rides, dark rides, and the zoo attraction.
Disney Springs:
1. Keep DisneyQuest, but completely remake it so it is extremely high tech.
General:
1. Expand the monorail so that theres an express line(Magic Kingdom, Transportation and Ticket Office, Epcot, Hollywood Studios, Blizzard Beach, Animal Kingdom), then another line(Epcot, Typhoon Lagoon, Disney Springs), then loops going round Disney Springs hotels, around Epcot hotels, and around Animal Kingdom and Hollywood Studios hotels.
2. High speed travel link between Future World and Tomorrowland.
