A better point is the game has changed either through necessity or design, neither automatically designates improvement.
In my opinion the game has mainly changes due to coaching tactics.
I'd be reluctant to fit that in under your heading of "design" because I don't think the coaches were standing back and looking at the bigger picture of how we want the game to look when they came up with their numerous tactics (for example the wrestle). What they were thinking about was winning games. Thats fine thats their job. But the last ten years have taught us lets not leave coaches in charge of the overall design of the gameplay.
There should be a committee of people who are solely interested in the game as a whole who are left in charge of the rules and NRL coaches should just about be seen as their enemy. It should be made up of people from lower leagues, high schools, Britain, France, PNG, NZs top league etc, that dude from Toronto etc.
You're problem is if you got your 40/30 this week you'd want 40/40 next week
I don't think so. 40/30 is enough to deliver a more adventurous style of gameplay. Wingers would absolutely have to get back and cover the repeat set threat for most of the set not just last tackle. Which is all we really need.