That is not an unreasonable accommodation until you have better solutions.
As an aside, we also know so much more about homework than we did just a couple of years ago. It's not very useful in most cases.
I would ask--what is the function of the homework, and then, can that be achieved another way?
https://adayinourshoes.com/iep-homework/
Now, about the rigid thinking.
I would start with being able to identify when he is using rigid thinking. I'm hosting a chat with an EF expert on tuesday, on the Facebook page.
https://facebook.com/adayinourshoesiep