6. Oz
Before I even begin on this one, I should say that from a legal standpoint this has little-to-no chance of inclusion in Kingdom Hearts III, but is included in the rare event that Disney and Warner Bros can settle their differences over the rights to L. Frank Baums Oz saga, which featured fifteen stories. As Warner Bros own the rights to the 1939 Judy Garland film, Disneys films about the fictional world, ranging from 1985s Return to Oz to Sam Raimis recent take on the material, Oz: The Great And Powerful, have had to tread very carefully about what they include, though the latter could fit into the Kingdom Hearts universe as a standalone story, allowing Sora and company to join with the eponymous Wizard to combat witchcraft. Without iconic characters such as the Tin Man and the Cowardly Lion, however, such a story may be somewhat generic.