Remember how it was said that to bring a person back you have to kill the Heartless first then the Nobody, if you kill the Nobody first then the body will fade away as it has no freed heart for it to inhabit. So what if in KH3 we kill Xehanort again and we get a new Nobody and Heartless wouldn't just killing this new Nobody first over the Heartless and poof problem solved
Remember how it was said that to bring a person back you have to kill the Heartless first then the Nobody, if you kill the Nobody first then the body will fade away as it has no freed heart for it to inhabit. So what if in KH3 we kill Xehanort again and we get a new Nobody and Heartless wouldn't just killing this new Nobody first over the Heartless and poof problem solved