What about reversing it...
Top 10 things league owes to rugby
1, Platform to 'invent' a new code called Northern Union (now RL)
2, Importance of goal kicking - Although there have been some good goal kickers throughout the years in many ways ex RU players such as Ridge, and Halligan turned 4 point tries into 6 pointers (or 5 points). No more toe hackers feature and all NRL clubs have 70% + goal kickers
3, Drop Kicks -1 pointers can be the difference between winning and losing
Struggling now ... help me out
Given RL was born in 1895 with a rule book and on-field game 100% the same as RU, then I presume for the sake of this argument you have to limit it to items RL adopted from RU between 1895 and today.
Which rules out Items 1 and 3 above (otherwise you would include the ball, goal posts, whistle etc).
In regard to Item 2 the accuracy in goal kicking is more to do with advances in the shape/technology of ball design, kicking tees and players being fulltime and thus having time to train. As a trend, NFL had round-the-corner "side-winder" kickers long before either of the rugby codes, and I'm not entirely sure who influenced Halligan and Ridge to adopt that style. It was in Sydney RL consistently since John Gray in the late 1970s.
The (now infamous) torso try rule appears to have been added to RL just after RU in the mid 1960s.
The five-eighth position was in NZ rugby before anywhere else in either code.
Differential scrum penalties.
Kicking tee (not sure).
