I should have clarified here. The homework I'm referring to is a "reading roll" (TP roll) onto which squares of paper are stapled with the assignment. At the bottom of each square, the student colors in a bubble everytime they practice it with parent and get it right (limit of once a day), then when they have 5 bubbles colored, they bring it in to the teacher to get a new square stapled. Many of these squares have handwritten stuff on them anyway that the teacher had to write on (address, birthday, phone number, a handwritten sentence to read, etc.). So it would be as simple as stapling on a different piece of paper once a week, skipping the easy squares for the advanced kids, or handwriting a different thing.

I doubt it is as simple as you seem to think to individualize them, but I have a different idea. I'm thinking that you might feel as though your son has to do this non-challenging homework because of the tracking they are using on it, and that's just the teacher's way of getting the parents involved and having a way to track that the work is being done, especially if a child ends up having difficulty even with doing the homework. How about suggesting to the teacher that you will try to adjust your child's homework so that it is more challenging, and when you are done with the assignment you deem more appropriate, you can still have the child color in one of the bubbles, and return that to the teacher.

There are a few lessons happening here, one of which is learning whatever is being reinforced with the homework, but another is that homework gets turned in, something that ended up being ridiculously challenging for my DS, and is not uncommon.

So it seems to me that you can meet your objective of having more challenging work that you can tailor yourself as you know your own child as well as meet the teacher's objective of the child learning to be responsible enough to do the homework, and then turn it in for credit.

I think this can definitely be worked, but I don't necessarily think it will end up with the initial solution you were seeking.