I like Puff6962's notion that the Losties are Others who were sent out into the world, have lost their way/diverged from their true selves, and were maneuvered (by the island?) onto Flight 815 to be brought back to the island, where they could attempt to rectify themselves, or like Eko, be judged failures and elininated.
I think Sayid will hook up with Nadia later in this season...
But, we have a flash of Jack as a young boy (when he got in a fight). That would mean that Jack got sent out as a baby, young boy, or something else.
Also, I think that you have to provide for some mechanism by which these guys lost their memories or diverged from their true selves. Alternate realities....and in this one they're lost....and with redemption they can unite with their "total" self spanning all realities. That would be a good use for the magic box and it would explain the other's incredible abilities.
I buy into this because of the russian guy's speech about being flaaaawed, weak, afraid, etc. You have to be perfected to be on the list and united with or become your true island self.
I don't know, Lion, was that what you were thinking? 
Ballpark.
Also, there seem to be multiple lists, not to be confused:
* The Flight 815 crew & passenger manifest, of which:
* The survivors, not all of which are:
* The lost Others (i.e. any Lostie with a speaking part), of which:
* Hurley, Kate, Sawyer, Jack, part of Ben's free surgery plan
* Ben's hit list (of island enemies?)
* Enlightened Others. Ben surely has listed them, too.
As for Jack's flashback to boyhood (I don't remember it specifically). You might also cite Hurley's flashback as a young boy (which I do remember). This goes to the thread of whether flashbacks/forwards are merely storytelling devices for our benefit, or impact the characters. If we say merely for our benefit, then still, a critical juncture is a critical juncture, whether it happened just prior to boarding the plane (i.e. Jin & Sun, or Sayid & Shannon) or back in childhood.
Do not forget:
Only a fool is enslaved by time and space!