You wouldn't step on them, of course. (They bite.) But maybe you could give them a high-five as you run the bases. Don't worry, baseball players; High-fiving a short person isn't any more strenuous than your average butt-pat.
#2: Spittoon Carriers
A small squad of short people carrying large brass spittoons could be employed to help keep the area clean. Different spittoon stations would include both dugouts, the bullpen, directly behind the umpire, and two "rovers". When somebody needs to approach the pitcher's mound for a strategy/spitting session, they would always make sure to bring along a spittooner.
#3: Proxy Base Runners
If a batter has a twisted ankle or a bum knee, that shouldn't stop him from participating. Just have a short person run the bases for him. Short people might take longer to cover the distance, but they're much harder to tag. Also, it would be easier for them to high-five the bases as they ran past.
#4: Proxy Batters
Yeah, Mr. Hot-Shot Pitcher Man, you just try to hit that strike zone.
#5: Proxy Pitchers
What the pitches would lack in overall speed would be more than made up for in pure anger.
Instead of learning countless hard-to-memorize gestures that can easily be thwarted by an errant bee or severe gastrointestinal problems, just use short people. Give a couple of short people little tablets and little pencils, and have them run your missives back and forth as fast as their wee little legs can carry them. "Messenger from the other dugout, coach. Apparently you're ugly."
#7: Good/Evil Consciences
You could dress them up as angels and devils, respectively. Each coach would have a pair, as well as the umpire and probably the pitcher.
Pitcher: "What do you think? Fastball?"
Short Person Dressed Like An Angel: "Yes, but not too fast. Give the man a fair chance."
Short Person Dressed Like A Devil: "I think you should bean him."
Wait, what? No. I mean . . . What? No!
#9: Proxy Fielders
Of course, you'd probably need about two dozen short people to cover the average baseball field. A whole new set of field positions would have to be created, such as left-of-center field, second-first baseman, and shorter-stop.
#10: Tackling People Who Rush The Field
The innate ferociousness of a short person could be leveraged to its fullest advantage. It would take an awesome level of inebriation to steel a potential field rusher to brave the lawn-piranha that was the Ten-Man Rush Squad, and they stop serving drinks after the seventh-inning stretch. (Note that "Ten-Man" translates into roughly fourteen short people, plenty enough to cover the field if positioned strategically.)