I have experimented with things like weights, checking, fighting, and aggression by isolating one variable at a time (the best I could). My goal is to improve the experience of playing against the computer. I wanted more hitting (both ways), more fighting, and fewer penalties. Here are my resulting ideas:
(1) When my team has some weight buggers, it is more fun for me to hit the computer. My purpose wasn't to make it easier to win, but it IS actually more fun when you can level guys. All of this we knew before. Maybe you didn't know that the computer's heavy guys not only go down easier, but, more importantly, hit me back more effectively. Here I did have to choose which teams I am more likely to play as (keep or even increase weight buggers) and which teams I am more likely to face (eliminate most weight buggers by notching their weight up a bit).
Another personal tweak was to make most of my checking line weight buggers. Since the computer will only match up checking line against your checking line when they are the home team, I could send out my checking line of weight buggers to smash their scoring line when I was the home team. I didn't want this line to become my best or to run the score up - I just wanted them to hit, so I lowered their shooting power and accuracy super low.
RESULT: The hits both ways increased, the crowd meter increased (which I am convinced does matter), and the fun factor increased.
(2) Because the checking rating in NHLPA is behavior - not skill (not the player's ability to check but his likelihood to check), I increased checking across the board so that most players were 60, 80, or 100. The net result did little to nothing to improve a team when I used it, but the team did make a better opponent. For teams that I wanted to be tough opponents, I made the majority of their players 100.
RESULT: They definitely defended against me better this way.
(3) I missed the NHL '91 fact that anyone would fight, so I increased all fighting ratings to 57, 71, 85, or 100. As noted elsewhere in posts, only a 71 or higher will start fights. A 57 will engage, though, and I did not let anyone stay below 57.
RESULT: I played 7 minute periods with line changes ON and was getting about 3 fights per game, a number I thought increased the fun factor without making it a game only about the fighting. Besides, now sometimes star player would have to defend themselves in a fight, but the goons were still the gooniest (100 fighting).
(4) I always like how penalties changed the flow of the game and made it feel slightly more real to me, but I always hated the pile up of players in the box with constant interruptions to call more penalties. Aggression, as far as I can tell, does NOT affect a player's likelihood to fight or hit (2 things that I did not want to lose); it ONLY affects the likelihood of penalties being called. I turned aggression down to 0 for all players but kept fighting and checking high. I also changed penalties to 1 minute for most, 2 minutes for a roughing that injured a player, and 3 minutes for fighting. Using 7 minute periods, I found this mix a perfect balance for my taste.
RESULT: The game had a few but not endless penalties, and the hitting and fighting were still high.
When I add in the fact that I play with medium or weak teams against stronger teams, the game has gotten much more fun for me.