I'm a broken record on this

but I think they should review everything upstairs between plays, and if they see something obvious worth overturning, buzz down and overturn it. If a coach wants to challenge at ANY time, fine. The review / decision is still handled upstairs. You lose a TO if you're wrong. You take a delay of game penalty if you're wrong and have no timeouts remaining. Maybe they up it to some sort of unsportsmanlike conduct on the bench if they're wrong X number of times. Fine. Coaches wouldn't abuse it when they still stand to lose TOs and/or yardage for being wrong. And reviewing / deciding upstairs, handled by people who know how to use the camera angles and replay system efficiently... wouldn't add any notable time to a game.
The way it is now, a single review adds a 3 to 5 minute delay almost every time. The flag gets thrown, the ref has to go talk to the coach, the ref has to announce what's happening to the crowd, the ref walks / jogs almost 100 yards sometimes to the booth, he puts a headset on and talks to somebody before he goes in, he spends up to two minutes in the booth, he walks / jogs all the way back, etc. etc. etc. They often go to commercial at some point. If you go to the games, you'll realize that sometimes they stand there waiting for TV to come back from commercial to announce the decision. It's ridiculous. Meanwhile, people watching the replay on the broadcast (or in the booth upstairs) often know what the call SHOULD be
before the coach has even thrown the flag.
