The ball is the key to everything. You want more balls in play? You want less strike outs? Lower the seams to reduce pitchers' ability to move the ball, and deaden the ball to reduce home runs. Adjust the ball's bounciness and settle in around 0.8 HRs per game per team (it was 1.4 in 2019) then guys like Didi Gregorius will start putting the ball in play more. (I'd like to see bigger ballparks, but that's not feasible.)