Would also love check-swing calls, even as a home plate ump you can still make a few judgments of egregious swing motions from behind the plate
In fact, I think that should be the challenged, since they are actually contested in MLB, unlike balls and strikes which are final, and you know, MORE conducive to be manipulated (as in the goal of this game)
(Also would love the Pat Moberg mode of just pursuing accuracy instead of being a secretly corrupt ump)