I hate the way rules are changed every year but one change I would love, which is not even a rule, would be for refs to decide to put an end to player tantrums and bullying behaviour towards refs.
There are some extreme examples, many starring JT, also Graham from the Dogs, but pretty much every match you ever see there is some amount of disrespect and shouting etc.
Instant penalty for backchat, 10 in the bin for abuse or aggressive behaviour to a ref.
It would be stamped out in about 5 minutes flat, and would be a much better look, not to mention it would give fans something better to emulate.