Sports experiments I would like to see

Baseball – Change to 8 fielders instead of 9.
The biggest advantage is it would reward hitting the ball, rather than waiting for either a walk or a pitch to slug, like the current system rewards. (So game would go faster, as a side advantage.) Great contact hitters like Juan Pierre, Michael Young, and Johnny Damon could legitimately be considered great players again, and Ichiro would possibly be the perennial MVP.

What would be the best way to react to this? I’m assuming have the pitcher cover first base? It’d be interesting to see what teams came up with. Other less drastic (but less fun) options are to make fields wider (but some stadiums would have to be altered), or possibly change rules about fouling balls off to stay alive (three foul offs and you’re out, or the ball has to move forward on a foul-off.)

Men’s tennis – only get 4 faults per game.
This change would be the easiest to implement and I think has real potential toward making the game more entertaining. You can go for big serves still, but not an unlimited amount. And if the game is dragged on in deuce, the advantage would shift to the fleet of foot. This could make things really enjoyable I think.

Basketball – higher rims and bigger penalty for fouling, maybe?
The combination of both of these could be interesting. Make it harder on players like Lebron to take it to the hoop, but also give a greater incentive to draw fouls—a free throw and the ball, perhaps. This would really be too much of a change though. I like basketball for the most part how it is.
(Except NBA really needs to get rid of the stupid “Timeout moves the ball to mid-court” that has hurt the last seconds of games since it was adopted in 1976. Last-second, full-court passes/drives are awesome! Look at plays #7-#3 here—and #1 if you’re a Duke fan. But yeah. None of these ever happen with NBA rules!)

Football – too many options to even consider
Football has a bunch of rules. Too complicated to try to change them!