I think you are making an excellent suggestion but students still can use ChatGPT before talking to ChatGPT to get highest grades.

Honestly I don't see the problem.

The students are cheating into studying more?

Homework and home assignments are not really a way to grade students. It is mostly a way to force them to go through the materials by themselves and check their own understanding. If they do the exercises twice all the better.

(Also nowadays homework are almost all perfect scores)

Which is why LLM are so deleterious to students. They are basically robbing them of the thing that actually has value for them. Recalling information, re-elaborating those information, and apply new mental models.