Charlie had to die because had he let the door open,Desmundo would have died too ergo no-one to warn the group. As for re-watching seasons,I've done it for them all and noticed small things(such as Chrisitan and the white shoe in the tree in EP 1) but nothing major. Here's why I think more than 6 got off:something I posted a few pages back:

1.) Jack
2.)Hurley
3.)Kate
Those 3 are self explanatory
4.)Claire and AAron-I believe Desmond's visions plus there are some peeps that benefit from staying on the island,Cliare is not one of them.
5.)Desmond-He has to meet Penny at some point,would be tragic if they didn't meet.
6.)NO IDEA.
7.)I think a seventh came back,Michael. It's the person in the casket of Jack's Flash forward.

I'd like to add a point here,the survivors are known as the Oceanic 6 right? They seem and from what has been said,actually are celebrities to some people. Soooo.... in Jack's FF,when he went to visit the casket of the dead person,why was there no big deal about this person? Was he not of the Oceanic 6?I say so because if they were celebs,surely more would have been made of the death?Look how famous Jack/Kate and Hurley were.

My guess is maybe a person from the island made it back,no-one knew about him,and he died.I'm going for Michael. The black neighbourhood in the scene and the camera on those big blac dudes was a give away imo.


That's my idea.Pretty neat if I say so myself.