Kingdom Hearts 3: 10 Disney Worlds That Must Be Included
6. Inside Out
A world exploring the psyche of Riley's mind would literally have limitless possibilities, and it's pretty clear that Kingdom Hearts has a big investment in emotions.
An even more interesting possibility would be to have the world taking place in someone like Sora's mind, with the cast of Inside Out making an appearance, but with the player controlling manifestations of Sora, Donald and Goofy.
Although that sounds like a big stretch, Square Enix have already been given a lot of leeway with both the Monsters Inc and Toy Story licences, which clearly shows that they have the power.
Whether the world takes place in Riley's mind or another character's entirely, one of the things that definitely needs to come over from the movie is the world itself. The story of Inside Out works pretty perfectly for Kingdom Hearts 3, but it's really the world possibilities that make it interesting.
Having the world take place in a character's mind means that it can literally contain anything that it wants to. Although following what happens in the movie would be interesting enough anyway, Square Enix could really go anywhere with the licence and that's what truly makes it exciting.