If i could change one rule in hockey it would be the number of players on the ice, i would make it so rather than being limited to 5 skaters and a goalie it would be a weight limit. every game players would weigh in before the game and the coach would have to make sure the players on the ice do not exceed the given limit, for example 1500 lbs. so if a coach wanted to put 15 children on the ice he could as long as they did not weigh more than 100 lbs each. on the other hand the opposing teams coach could play 5 grown men who each weigh 300 lbs. there would definitely be safety issues because of how much bigger and stronger some players would be but it would add a lot of strategy for the coaches and it would make any fights that happen during the game very interesting.