The Premise:
Characters are survivors of a plane crash on a mysterious island. Each of them has a Secret, and in the surviving luggage is a piece of evidence of what their secret is. As they explore the island, either as a group, or individually, they will slowly discover other people's secrets, and can use that information against them.

There is also another group of people on the island, the Others, who were there before the crash, and the Others have their own agenda. At some point, once all the Characters' Secrets are revealed, the Others make a deal with one of the Characters, who will betray everyone else, and then the game moves onto the second phase, where the remaining Characters try and figure out the Others Secret, why the Others are on the island, while the Betrayer falls back into a more 'traditional' GM role of providing adversity, controlling the Others.

Once the Characters find out what the Others Secret is... well, I don't know exactly. This is the part where I get stuck. I would say 'they then must defeat the Others and find a way off the island', and that might work, but it seems that maybe they might want to help the Others in their work.
-End Premise-

This was originally started as a board game, since I am much better at designing those than RPGs, but there are enough RP elements that I would rather it be an RPG, most likely with some board elements, to help with island exploration.

I want to figure out a way to add additional survivors to the group as well, and have them have their own Secrets, but I can't figure out a way to have Characters with Secrets added, and then have someone discover the Secrets, because my idea of Secrets is that there are item cards (board game elements showing through), so even when someone discovers a Secret item, they then have to find the person who has the Secret, and can use it to influence them, without everyone else knowing what the Secret is.

So my questions right now are:
a) What suggestions are there for an endgame? I want the survivors to eventually get off the island, and that be the end of the game, but between finding the Others Secret and getting off the island, I'm not sure where to go.

b) How does one add new Characters with Secrets and somehow be able to maintain those Secrets, but still allow influencing those Characters? And who should control the new Characters? People could control multiple Characters, but how do you play a Character who's Secret you don't know?

c) There needs to be other items in the luggage, and I can see having each person 'pack' their luggage as part of Character Creation, but there needs to be a limit as to what people can pack. I want it to be 'normal' luggage, so someone isn't packing a lot of survival gear and guns, but I do want guns to be a possibility. Maybe it depends on their Secret? Or maybe it depends on what their occupation was before the crash, so the police officer on board could have a gun? But I want most of the luggage to have some sort of survival use, even if it isn't obvious.

I think that's it for now. The idea has been mulling in my head for a while, not getting anywhere quickly, so I'm hoping the good people here at the Forge can help give me a push past this roadblock.

Maurice

Suggestion and a question.

Suggestion:  If you use the word "baggage" instead of "luggage" then you get double-meanings galore.

Question:  What's the intent of the game?  Are you looking to emulate the type of story that Lost tells?  Or are you using that familiar framework to do something deliberate, but different, of your own?

I certainly like the idea of baggage over luggage, I hadn't even thought of that as a possible double-meaning. So thank you for that.

I'm just planning on using the basic framework. I'd rather the Others have a much wider possibility of options, including maybe an evil cult, a research team (which they currently appear to be), an island of pirates, a lost prison colony, maybe even a tribe of cannibals.

'kay ... is the emphasis on the castaways trying to survive their own personal issues in order to explore the mystery of the Others ... or on trying to survive the mystery of the Others in order to explore their own personal issues ... or something else entirely?

I'm not 100% certain that I'm actually answering any of your questions with this, but when I read the bit about adding new Characters, I immediately thought of all the people that didn't survive the crash. Their luggage/baggage will also be around somewhere, so it's entirely possible that a Character finds a Secret of a Character that isn't being played. Meaning that there's always the uncertainty "Is this Secret I discovered even in play?"