So Sideways I'm Lost

SPOILER ALERT

From C.S. Lewis's The Voyage of the Dawn Treader:

"Child," said Aslan, "did I not explain to you once before that no one is ever told what would have happened?"

In this, the final the season of Lost, the creators have caught some flack for their new experiment, "flash sideways," explorations of what would have happened in a World Without the Island.  Ben sacrifices his ambitions for Alex's good; Sayid kills his brother's creditors; Jack works through his daddy issues; Locke comes to terms with his handicap; Kate lets Claire keep her baby.  Some people think this is lame.

A friend of mine suggests that he can't decide whether Jacob or The Man in Black is the real bad guy of the series.  I'm firmly on Team Jacob, but I am keeping my mind open.  Consider this, on the nature of literary tragedy:

After all is said and done, the audience should not feel impotent rage, denial, confusion or having been cheated. They should feel that the ending is a natural outcome to the hero's actions, and that in having faced punishment for those actions they [the audience] are purged of anxiety and worry. The world does make sense, the guilty are punished.

Is't possible that the purpose of the flash-sideways is to give us, the audience, a chance to see what would have happened if Jacob hadn't interfered with everybody?  Maybe the flash sideways are meant to telegraph the end of the series, to explain to us that the world does make sense and the guilty are punished.