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And by those I mean:
No shootout (a complete blight on the game, IMO)
No regular season overtime (leave it a creature of the playoffs where a winner is mandatory; same doesn't hold during the season)
No instigator rule
No delay-of-game rule for a puck going out of play without touching the glass/boards
Sky's-the-limit on stick blade curvature
No trapezoid / goalers are free to handle the puck as they will
What would the game look like today?
In my views, the first non-adoption (and to a large extent the second) means the now-extinct scoreless tie survives and with it, ties in general. The third may mean the players do a lot of policing themselves, which would indicate that diving will be dealt with summarily on the next shift or two. The fourth eliminates a ticky-tack penalty. The fifth probably helps scoring. The sixth may also help scoring if one has a Ron Hextall-like goaler.
Bonus if you can get the league to adopt review of the performance of on-ice officials by players and coaches such that the marginal ones find themselves riding buses in the AHL in the next season while the best in the AHL come up to the big time.