I think OP has made it clear that she understands about all the 'other' things at school, and has already completed those parts of the form referring to her child's social, emotional and medical needs. She is not trying to de-emphasize this side of things. She is merely asking for advice on the academic side, which counts too. Asking about the academic side does not mean she doesn't care about anything else!
Just because a child has complex needs does not mean their academics should be ignored.
Just because a child is academically very able, does equally not mean that their academic learning should be ignored.
OP, I think realistic asks for the academic side of things, for a highly able child with complex needs, is difficult to say as it is very rare. I think you won't be able to say beforehand which of your asks are realistic. It will depend on the school and their willingness, and ability, and resources.
So I would go about it differently: Rather than trying to determine what is realistic, go purely by your child's needs. Determine what is essential for him, and what would be really helpful, and what would be rather nice.
What does he need in order to learn?
(Being careful to consider developing depth of understanding also, not purely 'more' and going further through the curriculum.) What are the tools/conditions/resources/interactions he needs, to develop depth, and to progress in his learning?
This could be things like access to appropriate level books/textbooks for self study, access to computer programmes for self learning, space and time and quiet to follow up on his interests, a person who guides him through something/gently questions him, to develop deeper understanding, a feedback system, ... I don't know, only you know what your child needs in order to learn. And of course they won't be able to have this all the time, and much of the time the focus will (and should) be on other aspects, but provision should be made for him so that he too can develop academically.
Maybe for your child you need to point out that your child is perfectly capable of learning new things simply by being provided with the material at the appropriate level. But is not capable of getting deeper understanding of anything by doing lots of repetition/going over the same again and again/doing worksheets. So your child needs, in order to make academic progress, human help to reach deeper understanding of the things he can do already, or resources for self-study to push his learning further 'ahead'. (Just guessing here, you know best!)
E.g. one of my children learns brilliantly from being taught, the other learns only from figuring things out. The second needs opportunities to puzzle about and tinker with things (at the right level) or she won't learn. Explanations and even demonstrations don't work for her. The first needs explanations (oral or written), again at the right level. Luckily they are both within a standard range of ability, so they do get opportunities to learn at school without me having to demand their learning needs to be met, even if not all the time.
What would be helpful?
Perhaps there are things (approaches/resources/...) that aren't absolutely necessary to enable him to learn, but that would make the whole experience smoother and thus probably would be worthwhile not just for him, but also for the rest of the class, to have implemented. E.g. he learns best if someone checks in on him every few minutes to check comprehension. Or he learns best if left alone for a large block of time with feedback at the end. Or if he has 5 minutes of someone doing something with him 1-1, his learning will be equal to a whole day of group or class learning. Or he learns best if he can devote a whole day (or week?) to e.g. maths, then the next day (or week) to science, etc... or he learns best if he can frequently move his interest from one thing to the next.
And 'nice' are things that you could absolutely do without but would really make him, and you, happy!
All that said, unfortunately I believe it is rather likely that your child's school will ignore his academic learning until, IDK, secondary school or so. They will be highly interested in developing his ability to demonstrate his ability to pass the KS1 /KS2 SATS, but not interested in actually developing his ability further. Chances are that your 'He needs access to X in order to learn' will be met with 'He needs to demonstrate to us that he can do Y before we can do anything else.' Ensuring he has academic stimulation and continues to make progress will be up to you, I fear.