They need 1 more umpire. The 5th ump sits in the booth watching the game on the screens. He's in constant radio comm with the field umpires (well the crew chief at least). Every close play is automatically instantly reviewed, just like the NFL does now with TD's. (in case you didn't know that, EVERY TD is now reviewed, not just the last 2 minutes) No silly flags to wave, no challenges, no delays. The whole process will take 20 seconds. Baseball is perfect for this kind of replay because there is down time between plays anyway.
Also, the 5th umpire scores the game, thus eliminating this bs where the home team batter gets scored a hit or whatever to benefit their statistics. The way it is now, the official scorers are EMPLOYED by the HOME TEAM, which is utterly moronic and completely a conflict of interest.
Plus then the umpires get 5 guys in every game, which employs more of them, and their union will eat that up like my fish eat Prime Reef.