I think the rules should change every week, be it number of subs, goalposts and/or crossbars, players on the pitch, or whatever. Scoring should be switched up from week to week, as well as offside rules, passing rules, scrum rules, tackling rules, and so on and so forth. Before each set of weekend matches the coaches of all teams playing that week come together and take turns picking pieces of paper noting each rule adjustment out of a hat, just so everyone is on the same page.
However, there should also be one field of play rule picked by the referees that only the referees know, so that no one can anticipate plays or what may or may not be an infringement, just to keep everyone on their toes.
I call it Rugby Roulette.
das