I think the biggest issue that comes with the idea of an autistic character, lead or not, is Disney’s ability to execute creating a character with autism versus an autistic character. One has autism as a characteristic and the other has autism as the identity.
The other thing that becomes a hinderance is the spectrum of disabilities that fall into “autistic” tendencies. Everything from ADHD, OCD, Asperger Syndrome and many more are all considered as different levels of autism. Combine this with the fact that explicitly saying a character is autistic and it invites criticism and over analyzing said character to identify different tropes regardless of how accurate it may be.
On top of this I personally think there are already characters in Disney that have various forms of autism already. For example if we look at Ariel from The Little Mermaid an argument could be made that she seems to have Attention Defecit Hyperactive Disorder or ADHD. Collecting bits and baubles from the human world seems to take up all her focus at the detriment of other responsibilities such as her performing.
We could also look at Quasimodo as his physical deformaties may in fact lead to some developmental disorders that includes his speech impedement and the fact that he is a young adult who is still being taught his alphabet.
There are so many more characters that can be examined as such like Kuzco and his complete ineptitude when it comes to social cues. Dash and his seemingly ADHD tendencies. Even looking at Drax from Guardians of the Galaxy and his lack of understanding sarcasm is very indicitive of someone on the spectrum.
This all obviously is personal interpretation which then gets into semantics of Nature versus Nurture, the question of whether a person’s character and personality is innate or a byproduct of their environment. However the beauty of all of this that could be ruined by an explicitly stated “autistic character” is that kids with or without autism can find similarities of themselves in characters which may very well be taken away if Disney were to say, “Okay this is the character that is like you and all these other character’s are for normal kids.”
Again that is hyperbole but it very well may be what kids or parents of kids with autism interpret such as.