Re: Worlds of Kingdom Hearts - What worlds do you want to see in KH3?
The problem with having a ton of worlds is the threat of filler. What are we getting out of each world? What lesson is the character learning? Sora shouldn't have to be reduced to a supporting character while the main hero lives out their movie (Mulan, Simba, Jack and Will, etc). Each visit to each world should really mean something. I think the two games that handled this the best were KH1 and BBS.
In KH1, each world had something important to contribute. Besides the Keyholes, visits otherwise focused on defeating a member of Maleficent's cabal, encountering Riku, or the kidnapping of the remaining Princesses of Heart. The only filler was 100 Acre Wood, and would you want to leave poor old Pooh all alone, when he lamented being lonely and wondering what disappearing would be like?
In BBS, the Princess worlds adapted their movie's plots, yes, but the visits to each world largely focused on what the character was going through. Terra looking for true strength, Aqua worrying over her friends, Ventus looking for friendship and adventure, etc etc. Each world was a backdrop for the character in question's arc and contributed to it, for the most part.
While I do believe KH3 will have a ton of worlds, I hope that each visit really means something. That we learn something from each world, or that something significant happens in each world with maybe one or two at the most worlds being filler.
It would be interesting to see how the worlds react to Xehanort's threat. For example, would Emperor Palpatine decide to butt heads with Master Xehanort? Or forge a tedious alliance that both old geezers plan to eventually go back on? Elsa is for all intents and purposes a goddess, would Xehanort target her to make her a Seeker of Darkness or at least turn her into a Heartless and Nobody? Would Wolverine be sought out as a bodyguard for the Princesses of Heart by Yen Sid?
What if Xehanort begins competing with Maleficent for Disney Villains? What if Xehanort intends to recruit Disney Villains and their forces to have at his disposal in the final battle?
There's so much that can be done with this universe and the vast library of properties Disney has, bolstered in recent years by their acquisitions of Pixar, Marvel, and Star Wars. Hopefully the worlds chosen truly serve a purpose, and are relevant to the overall story somehow.