Changes I'd like to see:
The law on head high and tackles in the air be scrapped. There are many times when these tackles are technically illegal (a player tackled when about 3cms in the air, for example). Simply have a law that bans dangerous tackles and allow referees to have discretion.
Make a dropout be made from under the posts. I see no sense in a team gaining a 22m advantage simply by grounding the ball behind the goal line.
It's not giving the team now in possession an advantage, its punishing the team that kicked for not getting the kick right. Remove that, and teams can kick all day in expectation of superior territorial gains, because its now a lot easier to get it right. Not a fan at all.
Change the offside line from the hindmost feet to 10m back from a ruck or maul. This would open the game up considerably.
One quick ruck will put almost the entire opposition team offside. That's unplayable.
The obvious counter is for the defence to never put in anyone other than the tackler, thus avoiding the creation of a ruck or maul. I don't think that's a good thing to encourage.