Two changes.

1. Allow penalty advantage. Often a teams momentum is stopped as a result of being awarded a penalty, allows defence to reset.

2. In close matches, Ive seen teams deliberately slow the game and concede penalties in the last minute to run down the clock. Allow the team in possession to finish a set. Obviously carry on if a penalty is given which restarts the set

Reduce the interchanges.
Have the same set of rules for all domestic competitions and international across the world.

I have wondered about having a 3rd, Regal Trophy, competition and reducing the SL fixtures to a simple play everyone twice.
The new competition would be played with 2 subs and only 2 or 3 interchanges (old school). I also thought we could use the 5m rule and push for a quick PTB, meaning a fast flowing game but less effect for scooting hookers and 5 drives and a kick rugby. This might encourage a bit of old school guile coming back into the game, whilst also minimising the physical wear and tear of an extra competition.

add 2 players per side, kick and chase, and a line out - NOT A CHANCE!

Kicking dead should result in a restart on the 30 or 40 maybe.
Get rid of scrums or change it.
All rules the same for all countries and comps.

Also. If a try is scored against Australia. It shouldn't be disallowed. Kind of gives them an unfair advantage.

Also. Shoulder charge brought back. Just give harsh punishments for head shots.