College football has replay correct. A fifth indvidual in a booth with the advantage of HD instant replay for home runs, fair foul, trapped, intereference, safe/out, most everything but ball/strike. Ball/strike remains with the umpire on field.

In actuality this will speed up the game. Instead of putting up with a player/manager tirade and the delay that occurs the booth umpire can signal down and confirm or overturn the call. Once the booth officia has made the call any continued complaining can be met with immediate ejection/potential suspension. They don't even have to take time for all four umps to walk off the field.

This isn't rocket science. We have the technology.