I've put together a straightforward plan for TWDC/WDI to "fix" Future World - everything here can and should be implemented by EPCOT 50, and imo, nothing on this list is a stretch (steps are in order of priority):
Step 1: Repaint the Imagination pavilion, fix the jumping fountains, wash the glass pyramids. Then, gut the current version of the ride, and use one of the many fantastic proposals that have been suggested here to restore JII as closely as possible to the original ride - many of these proposals even use the current track layout and the creative use of a preshow to simulate the original turntable sequence. Put a new film in the Magic Eye Theater - it can be media-IP, doesn't matter, anything's gotta be better than Pixar Fest.
Step 2: Put Inside Out into WOL - create a version of Cranium Command using the movie as a basis. Fill the pavilion atrium with various flatrides and a couple of shows. Use of the Body Wars space is optional - could make the former queue space a meet and greet or something.
Step 3: Gotta address Mission: Space - I think there are two options here, and one is significantly easier than the other. First, rename the ride Horizons: Mission II. Then, you're gonna rework the queue to be heavy on the Horizons theming. The ride itself is going to use the same system, but a new film will take guests through space to Bravo Centauri, then to Nova Cite, Mesa Verde, and Sea Castle. Second option is to gut the ride and recreate some sort of sequel to Horizons - I think the first option is much more digestible and would breathe some new life into the pavilion.
Step 4: The Land is mostly fine, but can use a few tweaks. Inside, refresh the theming a bit - get the weather balloons moving again, add some life to the paint scheme (murals or something). Then, you're gonna scrap Awesome Planet, and replace it with Kitchen Kabaret 3D (or 4D). The whole thing can be a 3D (or 4D) film, and maybe just add a Bonnie Apettite animatronic into the theater for some depth. This is a nostalgia layup. Keep the carepeted walls in the lobby, but add some of the revue theming to evoke the old Kabaret lobby. The rest of the pavilion is good to go - maybe add the "Listen to the Land" song back and change the lyrics to "Living with the Land", another layup.
Step 5: The Seas can stay Nemo, that's fine. Just one change - get rid of most of the sets throughout the omnimover portion of the pavilion, and restore the view to the aquarium. You can even retain projections of Nemo characters throughout the entirety of the ride, similar to the ending portion of the current version. Instead of spouting mindless nonsense, the Nemo characters can educate guests about their fishy friends swimming around the Seas. SeaBase can stay the same, just clean it up a bit.
Step 6: Spaceship Earth needs attention, but I'd argue only from an infrastructure standpoint. Do NOT touch the show scenes - if anything, shut down the ride, fix the track, maybe bring in some new ride vehicles. Touch up the descent with some new scenes, and update the Global Neighborhood. The new cocktail lounge will round out the experience. That's it though.
Step 7 (Optional): Instead of using CommuniCore hall as a collegiate dining hall, throw a few exhibits in there that call back to the original CommuniCore/Innoventions. I really can't see them doing this, because they "need" festival space, but it's worth exploring - maybe only roll out exhibits during the offseason? Also, get rid of that stupid planter in the middle of the new spine and bring some sort of fountain back.
That just leaves Cosmic Rewind and Test Track. The latter is currently being fixed and should reflect what we all want, so I'm not going into details there. Cosmic Rewind is difficult - on one hand, it's currently based on a popular IP. But give it 10-15 years, and I'm not sure how culturally relevant GOTG will be. When the day comes to refresh the pavilion, I would create a spiritual successor to Adventure Through Inner Space - this is not my idea FYI. Rather than being teleported, guests are shrunk to the size of an atom. The ride itself is a whirlwind through atoms, culminating in a loop around the nucleus of an atom, rather than the moon like in the current version of the ride.
And that's about it. Best part, I think all of this can be done for a reasonable amount of $$$, and in just a few years MAX - maybe even before they break dirt on Coco at DCA. I'll take my check now, Disney.