What if they got students, at the start of the semester, to write a few non graded essays under strict supervision, then use this as a guide on their natural writing style?
Then, if some assignment has a different writing style, not only could that potentially detect more simple uses of AI, but it might detect the old trick of getting their friend to give them a copy of last year's assignment and passing off that work as theirs, since their friends writing style would be different.
Of course, if the student is smart enough to train the AI on their own writing style, this might not work so well.
But it might help get a guide for people who naturally write in a way that will get flagged by these tools, such as Neurodivergent people and hopefully prevent them from being falsely accused, since it would already be known from the start that this is their natural writing style.