How about you stop assuming and research the actual data? The pitch/fx tool includes the famous "grey area" about the size of a baseball all around the strike zone. So no, said "grey area" would not bring the strike zone mistakes under 10%. What would do that is if umpires actually stuck to the rulebook, instead of having personalized strike zones like Angel Hernandez.
Also, a couple years ago, replay was a "pipe dream" that "MLB would never go for" because the "umpires would never allow it". MLB can implement whatever rules it wants, and unlike the players, the umpires' union is not powerful enough to do anything to stop it. If it were, we would not have instant replay.