With respect to the football, a rule change I would introduce would be to make waving an imaginary card an automatic booking.
The play acting is frustrating but nothing much can be done about it as it’s subjective. Alonso, quite clearly, had every right to stay down after the above challenge. Villa actions later on, however, were quite frankly pathetic.
One solution could be a rule requiring a player who is writhing on the floor in agony having to spend 5 minutes off the pitch for each role he makes after the challenge, regardless of whether he’s recovered the second he gets of the stretcher/over the whitewash. That should see some of the ridiculous tumbles worthy of a gold medal gymnastic routine diminish in due course.