Eliminating Boone and Shannon, Fine. Jin and Sun? I can see an argument for that (but I wouldn't like it). But no Charlie, Claire, Hurley, and Desmond? That's ridiculous. They're all core characters.
That being said, I can't see the show being one season anyways. Sure, there's a lot of filler and side adventures that can be cut down, but a lot of the substance of the show would be lost (no pun intended), particularly the flashbacks.