Well I haven't had much time to consider, but I'm guessing some circumstances would be "reviewable" and others not, as in throwball.
If the whistle is never blown, there's nothing reviewable there. If the whistle does blow for a penalty/dive, a 60-90 second clock from upstairs could give plenty of time to review, and follow the NFL standard of "indisputable evidence" from there to either stick with or reverse the official's decision.
I'm not 100% convinced this would be good policy, but as I said initially, I'm not immediately against the idea. The game moves so quickly, and referees have a very tough task on many penalty decisions, especially in a crowded box or on the break when the official's sight lines aren't perfect.