Everyone knows what a close call is, they should just have someone in the box of each game checking EVERY close call. There is generally plenty time between the end of one play and the start of the next AB to figure out if a call is correct (things like the Melky play at 1B that was CLEARLY an out).
Give the head ump an earpiece to hold the next AB if there is a call that requires additional review (like Colby's HR).
Keep the managers out of it. They are the problem, not the system.