That would be hilarious. House-elves could be very clever, but they are obsessed with particular topics. So EY could write them as excellent rationalists who are focused only on Hogwarts matters, and as excellent rationalists they would set up prediction markets about various predictions (students' grades, their cleanliness, relationships, popularity of reducing the salt in the mutton, etc.)

I'm afraid you don't get to call it because your comment might inspire EY to add them in the first place. :)