Great article covering MLB's experimental rules in the minor leagues and the effects (positive & negative) they had.
Several minor leagues served as the guinea pig for ideas that could improve the pace of play, including robo umps, pushing the mound back, and bigger bases. Were they effective?
www.theringer.com
"The AFL (Arizona Fall League) is using the ABS system (in games at Salt River Fields), the full shift restriction, the 15-second pitch clock, the pickoff-attempt limitation, and the 18-inch bases, which may hint at the rules that MLB considers keepers.
MLB wants to ensure that “the call that ABS is producing matches the representation of the pitch location on all our different platforms,” so that a strike on the field also looks like a strike on K-Zone and Gameday (and vice versa). For that reason, Sword says, “We’ve been prioritizing rectangular, two-dimensional zones as we work through this process.”
...a 15-second pitch clock (17 seconds with runners on base) in the Low-A West, a circuit composed mostly of teams from the former High-A California League. After the pitch clock started ticking on June 8, the league’s average time of game fell by roughly 20 minutes, from 178.2 minutes to 158.4.
Because the (step-off) rule wasn’t paired with a pitch clock, it also led to long delays as pitchers held the ball to try to disrupt runners’ timing, usually in vain. Although steals were much more common, Goldberg-Strassler says, “players were frustrated and the larger reaction from spectators was that games/pace was slower than it had ever been.”