All instant replay reviews are examined by an umpire at the Replay Command Center in NYC, who has the final decision as to whether to uphold or overturn the initial call.... but I think your point is for the Command Center to call for the replays?
I don't see that as a current issue, as Managers are going out to the field on every close play... waiting to hear from their bench if they should challenge.
To me, the biggest current issue is game play.
Yeah, have the central office call for replays but give on-field umpires the power to call for them as well. Coaches wasting time until they get the thumbs up is dumb, players will always think that they're correct, and umpires will never say they didn't get a good enough angle to make the call. Think about how often the umpires get together on the field and overturn a call as it is. The most efficient way to get the right call is to have a centralized body call for the review and make a decision in, like, 30 seconds.