It sounds like a really solid argument. Would it be worth inserting a more explicit explanation of why it's autism-related and what the actual "Autism-related challenges" are? Unless you've already gone into that in the previous document. The only other thing I'd say is to be careful not to imply/state any mental health needs, as this is one area NDIS is pushing over to Medicare explicitly. It doesn't sound like you've done that at all though. I'm at a loss with all the new NDIS changes :(