The league didn't worry much about pace of play when they jammed 9 official TV timeouts into each game. What's better than watching players milling about, ready to play, simply standing around waiting for a red light to turn off? Obviously, what they meant to say today was, they're worried about slowing down the game for things that don't line their pockets with cash.
I'm only talking about giving each coach one challenge per game. They'd have to use it wisely at a crucial point in the game. If they use it, for whatever reason, on a play that isn't close then the replay delay won't last 30 seconds. On close plays that could decide games, I have no problem stopping down for 2-3 minutes if the referee appears to have blown the call.
Instead, the league would rather let referees revel in wrongness. The league seems completely unaware that everyone in North America has their own replay booth at home now - crystal clear HD that you can freeze frame and rewind over and over. The fans are all getting the crucial calls right. They're infuriated when the refs slaughter those crucial moments. How is frustrating your customers good for the game?
One replay challenge per game to each coach. Challenge anything. Controversial goals. Controversial penalties. Whatever. Just get it right.