What I want (that does not mean they are the only things that should appear):

Main Cast:

Sora, Riku, Kairi, Xehanort, Mickey, Donald, Goofy, however they appear or reappear Terra (Enigmatic Knight is possible who is restored to the full Terra after Xehanort's destruction), Aqua, Ventus

Worlds, Heroes & Villains:

Destiny Islands
Disney Castle
Twilight Town
Traverse Town
Radiant Garden - probably Squall and Maleficent
Keyblade Graveyard
Middleton - Kim Possible, Dr. Drakken, Shego
Olympus Coliseum - Hercules or Zack, this time as reawakened ghost like Auron, not like in Birth by Sleep, Hades
The Incredibles' version of the United States - Mr. Incredible, Syndrome
Port Royal - Captain Jack Sparrow, Davy Jones & The Kraken, Captain Edward "Blackbeard" Teach
Neverland - Peter Pan, Captain James Hook
Jungle Book could be okay, but is replaced by Deep Jungle and Pride Land anyway

MAYBE Star Wars now that it is owned by Disney.

and many more. The worlds I have mention should show more characters their respective story, of course.

Final Fantasy Cast:

V. Bartz, Faris, Lenna, Galuf and Krile appearing in Port Royal on the Fire Ship
VI. Terra (appearing as "Tina"), Setzer
VII. Sephiroth, Cloud, Aerith, Tifa, Cid, Yuffie
VIII. Ultiemcia, Squall, Rinoa, Seifer, Fuu, Rai (Twilight Town versions), Seifer, Fuu, Rai (alternate universe, the original versions of them known by Squall), Selphie (Kairi's friend), Selphie (alternate universe, 17 years old and Squall's friend, the original Selphie)
IX. Kuja, Zidane, Garnet, Vivi (Twilight Town version), Vivi (alternate universe, the original Vivi of Team Tantalus)
X. Seymour, Tidus, Wakka (Sora's friends), Tidus, Wakka (alternate universes, the Final Fantasy X heroes), Yuna, Rikku, Paine (fairies), Yuna, Rikku, Paine (alternate universe, the original versions)
XII. Vaan, Penelo, Balthier, Fran
XIII. Caius, Lightning, Serah, Noel, Snow

Villains:

Sephiroth, Ultimecia, Kuja, Seymour, Caius

Of course even those I have not mentioned as alternate universe ones have not exactly the same story they have in their original Final Fantasy but those I have mentioned are totally different so I want them to appear in two versions and that can also something cool and new for Kingdom Hearts.