Final thoughts before the last season starts...
As the final season of LOST is set to begin in mere hours, please allow me to share some last-minute thoughts.
1) If I had to pick one theme from the show to call the strongest, especially in light of the last two seasons, I’d have to choose “None of the main characters learn anything.” For example, Jack eventually opts to detonate a nuclear device on the island because he can’t stand that he lost Kate. Really, a character can’t get more loathsome than that, risking the lives of others because he can’t live with losing a girlfriend. Also, John fails at everything so badly that many viewers predicted he’d die. Desmond has no significant reaction to Charlie’s death even though it appeared meaningless in spite of Desmond’s claim that it would save everyone, including Claire. (Even if this is something yet to be (which would make no sense), there’s no reason for Desmond to be confident of that at this point.) After Sawyer kills John’s father, his character stalls and meanders in fairly illogical ways. Kate grows into motherhood, but otherwise seems never to develop into anything new. Many interesting things going on between Sun and Jin have completely stalled.
2) A key supporting role has also had a very disappointing arc. Ben, at first shown to be a master manipulator, is, in the end, reduced to a fool who barely seems capable of the genius that was ascribed to him in earlier seasons. It actually started in season 3 when John stole a tape recorder from him… after Ben had cruelly provoked John into leaving the Others’ camp… and shown John precisely what was on the tape and where he kept it hidden. And then Ben was surprised it was taken? Lame.
3) The only way I can think of to “fix” #1 is to suggest that the lack of character development was deliberate in order to justify the necessity of all of the characters going back to try again. This isn’t much of a fix in my opinion, but it would help some.
4) If Dan was right about what the bomb would accomplish, then, indeed, the characters will have a chance to try things again.
5) They could pull an old “Dan caused what he was trying to prevent,” but that would be very lame. Surely Dan, his memory problems and obsession with Charlotte notwithstanding, would have considered that possibility and taken great pains to know beyond a doubt that the “detonate a thermonuclear device” trick had not yet been tried.
6) The only way to “fix” #2 is for Ben to have been in on Jacob’s plan all along. Meaning Ben would have been conning the “fake John” in the final episodes of season 5. While this would be somewhat predictable, it might be kind of awesome given Michael Emerson’s acting abilities.
7) If Dan was right (and, remember, the story would be lame if he wasn’t) then a new timeline has been created such that the Island does not have a Swan Station. This may be the only major change to the timeline. (Since the blast was supposed to neutralize the energy pocket, it follows that the energy pocket may have neutralized some of the blast, so that the rest of the Island and much of the Dharma Initiative might have survived.)
8) Without the Swan Station, there is no button that Desmond is destined to push. HOWEVER… Widmore may still have a reason for sending Desmond to the Island. And Jacob may have some other way of getting all of the crash survivors onto the Island. So those things need not change in the new timeline. Desmond and the Flight 815 folk might still end up there.
9) So… why all that work just to create a new reality where the Swan doesn’t exist? Perhaps because the Swan was THE major tripping point for John. He wasn’t supposed to be distracted by it. In fact, at one point he was supposed to follow signs related to the drug plane. But he ignored those signs in favor of “the hatch”. Perhaps John is the key for everyone else getting things right. If so, removing his major obstacle will help everyone.
10) If Ben’s murder of Jacob is a ruse, then… what’s the point of it? How does anything that happens in 2007 matter if Dan was right and Jack was successful in changing things? The events we see in 2007 can’t be on the changed timeline. Although we do see a photograph of Jack et al from the past, the 2007 timeline is clearly consistent with one where no bomb has been detonated… for example, Ben and “fake John” note the blown hatch from the Swan sitting on the beach. So what gives? Well, assuming that Jacob and his enemy aren’t subject to changes in the timeline and, therefore, see all iterations, the interaction between them stays relevant. Perhaps Ben’s participation in Jacob’s murder actually helps Jacob and Ben in some way that Jacob’s enemy doesn’t realize. What way would that be? The only one I can think of is that perhaps Ben’s stabbing of Jacob somehow allows the three of them to jump onto Jack’s new timeline, and this somehow takes power away from Jacob’s enemy, since, presumably, in the new timeline John isn’t such a dolt. Of course, you’d think Jacob and his enemy would have an easier way to jump from one timeline to another… or that, perhaps, there’s a version of them both on every timeline… and there’d be two Bens on the new timeline, right? But… this just sounds like something the LOST writers might try.
Anyway… those are my thoughts. Enjoy tonight’s premier, everyone!

Final thoughts...
I haven't watched yet. I have a classthat I don't get home from until late on Tuesdays so I'll have to watch online Wednesday. These are a few thoughts in reaction to what you posted:
1) I agree with that theme and the one that seems most irreedemable to me is Jack. I generally think the writers have gotten offtrack with some of the romance narratives--relying on them too much for motive and having them keep the characters too defined. The character I see with the most potential for some kind of turn around explanation is Desmond. I think Desmond is the key character to me and the fact that he was so under utilized in the last seasons stands out like a sore thumb. So I'm thinking that something has to happen with Desmond if the show is going to work.
2) & 6)Yes--the only hope here is that is it a double bluff. It seems to me that there must be something going on in which Jacob actually wanted to be killed. There's some repeat of things over and over that Jacob and Smoke/The ManinBlack are engaged in that Jacob is seeking to change in being killed.
9) No Swan Station--no Desmond pushing the button over and over, no Desmond consciousness travelling. There's also the theory that Lost Connection had that pushing the button actually changed Desmond through exposure to the radiation.
I think that Desmond's ability to mind travel--something that no one else on the show has been shown doing yet--is somehow going to make him the one who connects things--across time, across realities, whatever it is. He's the pilot. (And remember, there's a big clue in the pilot :-)