Flash Sideways are the Original Timeline by haveyoumetandy

What we've been seeing in the "flash sideways" is actually the original timeline. By that I mean that in the flash sideways, the characters will make a conscience choice to come to the island by allowing themselves to be placed in what we think of as the main timeline.

Similar to Dogen's story, what if Jack drinks too much and ends up putting his son's life in danger. At this point, Jacob can come to him and tell him that he can save his son's life if he agrees to come with him and never see his son again. But here, Jack isn't taken directly to the island, instead he's put into the main timeline we've been seeing since season one.

The other major characters may have made similar deals with Jacob. Sayid must agree to a life without Nadya and Locke has to live without Helen, both by being placed into the alternate timeline. Now, both Sayid and Locke had Nadya and Helen, respectively, at certain points in this original timeline. However, I think they are put into this timeline at the time Jacob touched them in the incident. Thus, Sayid is placed in the timeline almost immediately after Nadya's death and Locke is placed in after it's over between him and Helen.

I'm not sure exactly where Kate, Hurley, Sun, and Jin fit in but their sacrifices may be explained later.

I've had a hard time accepting the flash sideways, but if we see the characters here making a sacrifice to be put into the main island timeline, it would actually make the flash sideways a lot more interesting.