Michael/Kevin?

I would say Michael. Remember in the last episode when Locke asks Ben who his man on the boat is, and Ben says that he'll tell him but he's going to have to sit down first or something like that. It's probably because Locke is going to be surprised that Michael somehow ended up on the freighter.

Definitely Michael

Regina.... yeah, she went nuts but she knows to not trust the captain for some reason. Maybe that is why the captain was ok with loosing her...

I sort of hope it's Lapidus. I want him to be a good guy.

I think Lapidus will be a hero in a critical time. He IS cool.

Michael, on orders from Ben.