1. Make the exam the only thing that determines the grade (or technically, proves that the student learned enough);
2. Give out test assignments students can do, but don't have to;
3. Offer students for the professor to grade their work if they want to get some feedback on how they're doing.
Would that lead to less time wasted by tutors grading AI generated answers? From where I stand, students should be allowed to prepare for exams any way they like, with or without their professor's help. If they managed to learn, they pass.