Rather than expand the balk rule to include the little-used fake-to-third, throw-to-first maneuver, why not get rid of the rule entirely? Let's ask the Moneyball question: If we weren't already doing it this way, is this how we would do it? Not according to Bill James:
The [balk] rule manifestly fails to achieve its goals. It's one of those rules that, when it didn't work, they tried to fix it. When that didn't work, they fixed it again, and they fixed it again, and they fixed it again. At some point they should have stopped and tried something else, but they didn't, so they stuck history with a rule which (a) is almost totally unintelligible, and (b) is arbitrary in its enforcement. In principle, trying to prevent one player from decoying another is a dumb idea. The balk rule is like a rule in basketball that says (a rule that would say ... theoretical example) that if you fake a shot, you have to take the shot; otherwise it is travelling. That would be a dumb rule. The balk rule is basically the same thing, only applied to baseball.
Here's another question: Why was this such a priority for MLB that they implemented it over the objections of the players? If the goal is to shorten the games, there are dozens of things you could do, starting with enforcing rules already on the books:
When the bases are unoccupied, the pitcher shall deliver the ball to the batter within 12 seconds after he receives the ball. Each time the pitcher delays the game by violating this rule, the umpire shall call Ball.
The batter shall take his position in the batters box promptly when it is his time at bat. (b) The batter shall not leave his position in the batters box after the pitcher comes to Set Position, or starts his windup. PENALTY: If the pitcher pitches, the umpire shall call Ball or Strike, as the case may be.
Rule 6.02(b) Comment: The batter leaves the batters box at the risk of having a strike delivered and called, unless he requests the umpire to call Time. The batter is not at liberty to step in and out of the batters box at will.
Maybe MLB wants less booing at the ballpark. Whenever the visiting team attempts the fake-to-third, throw-to-first move, the home crowd boos. But if it's booing you can't abide, why not do something about intentional walks? Fans really hate intentional walks. Why is MLB taking the bat out of the hands of Joey Votto and Prince Fielder?
It probably wasn't the boos. But what was it? Why do this? Such is the inscrutable nature of Major League Baseball in the Selig era: Ignore the real problems and hope no one notices. And copy everything the NFL does. There's literally nothing wrong with baseball that couldn't be fixed by adding like ten more wild cards.