The title is self explanatory,
Sora, Riku, and Kairi as playable characters. Blending in BBS and DDD. Except this time, we switch by CHOICE. Each exploring a different time period in each world.
Kairi the only one who travels through worlds on her own. Donald and Goofy (and Jiminy too) traveling with Sora, Mickey traveling with Riku.
In case it's not a numbered title, here's how I think the gameplay could work. Keep the combat similar to the numbered titles. And the abilities are unlocked through spending AP in a skill tree (almost like in Re: Coded and DDD).
Ties to the Timeless River door appearing to Pete. And Mickey, Donald, Goofy, Chip, and Dale's trip to Daybreak Town.
Returning worlds: Traverse Town, Neverland, Atlantica, Pride Lands, Radiant Garden/Hollow Bastion, The Land of Departure/Castle Oblivion, and Daybreak Town/Scale Ad Caelum. New worlds: Gravity Falls, Shuggazoom (SRMTHFG), Bambi's world, the world of Meet the Robinsons, Hawaii (Lilo & Stitch), and the galaxy of Star Wars.
Maybe they won't use all the worlds listed above. If they use that number worlds (along with a final level kind of world), leveling up should take longer than in KH3.
To keep it simple for Yoko Shimomura. She should try a more tropical remix of the music used for Deep Space. To fit Hawaii's setting.
If past versions Cid and Tifa appear. They should be designed to how they looked in Final Fantasy VII. That means white tank top.
Imagine how the present day Kairi would interact with her kid self (from before her abduction), or Namine (before she caused Aqua's short lived reunion with Terra in 0.2).
The future time periods of Neverland, Atlantica, and Pride Lands occurring simultaneously with Return to Neverland, Return to the Sea, and Simba's Pride respectively. Just like Kingdom of Corona, Arendelle, and The Caribbean.
The final battle set in the night Destiny Islands fell into darkness. With a time travel game, what better setting than the aforementioned event?
What do you think?