Major flaw in the storyline: I just got attacked by a shark on a huge cruise ship. My friends and family are dead. I'm depressed. I'm stuck with a bunch of strangers on a godforsaken island wondering how I'm going to survive. Oh! Thanks for the money, captain! Let me go buy something from that monkey over there! Not quite. Also, if there even is a 'civilized' portion of the map who is capable of developing modern weaponry- wouldn't they also be capable of scavenging the ship, or receiving a distress signal from the ship in the first place and bring those guns and save the day?

That sort of defeats the whole purpose, even if part of the island is uncivilized. There would have to be a pause in time, where it fast forwards to months later when a small civilization created from the survivors where the player is maturer and better skilled in combat and ready to start his/her way in being an active contributer to the small society. There's no guns. If there were any on the ship, they ran out of ammo user defend from the tribal groups. Now they're entirely defenseless and have to learn to adjust to survive like the natives do. There's also not a whole lot of theft between the group. In order to survive, the survivors had to learn to work together. In the time since the disaster, they've created intimate bonds with one another as a small community, with the captain as governor. You see this as the player interacts with NPCs and everyone seems to be acquainted and familiar with one another at this point. Now, if you still want there to be theft, steal from the natives. But make sure there's also an alternative to encourage players to also help build tribes and even become apart of them (as you mentioned). Tribes would become an equivalent to AP, except there's more than two extremes as there are multiple tribes. There has to be benefits to each one, so players aren't all compelled to jump to one side and leave the rest blank. The more options and opportunities, the better.