Alternate Timeline misconceptions by Sam

Most people have been making an awful lot of assumptions about the alternate timeline, and I think that most people have got it wrong.

There are two options concerning the alt. timeline:
- The timelines were identical up until 1977, and then split into two (this theory I shall call the "After" theory)
- Jughead caused the change to happen before 1977 because the Losties never travelled back in time ("Before" theory)

Most people are assuming that the latter theory is correct, but I'm fairly confident that the writers are going to choose the former, and here's why:

Proponents of the "before" theory assert that the "after" timeline is paradoxical, as if O815 didn't crash then Sayid could't have shot Ben, Locke couldn't have visited Richard, etc. But this scenario actually isn't paradoxical at all. The alternate Sayid doesn't have to travel back to 1977, because the original Sayid has already done it. The alternate timeline was created by the actions of the original Losties in 1977, and so they must remain in the timeline if they are to cause the events that stops the plane from crashing. If anyone can explain to me why this scenario is paradoxical, I'd be happy to reconsider.

The "before" theory, however, is more paradoxical. The bomb causes the new timeline, which stops the Losties ever coming to the island, and so the bomb never goes off, which means that the plane still crashes, etc. It could be argued that the universe course-corrects to create another event that stops the plane from crashing in the alt, but this would be far more complicated and much more difficult to explain.

One argument used by "before" theorists is that if the bomb goes off, then Ben, Ethan and Dogen should all be dead in the alternate timeline. But why does this have to be the case? Couldn't the bomb simply have neutralised the energy underneath the Swan, like Faraday said? Or maybe the bomb didn't go off in this timeline (maybe the bomb going off was actually the incident in the original timeline), which meant that the energy was never neutralised. Whatever the bomb did, this event then led to the island sinking somehow at some point between 1977 and 2004 (although I have no idea why!), giving people a chance to escape.

Let me put it this way - what happens the second after Juliet detonates the bomb in the alternate timeline? In the "after" explanation, the Dharma folk would see the Losties disappear, the bomb stops the incident (or whatever), this leads to Ben and Roger leaving the island and the island eventually ends up underwater. But in the "before" theory, this is much more difficult to explain. Do the Dharma fold suddenly gain new memories in which the Losties were never there?

OK, so that's my theory of what happened (or what didn't happen) after Jughead went off. So I ask: why should I believe that the Losties were never there in the alternate timline, as most people are assuming?