Since they're all supposed to be fairly average, perhaps one of the characters is apart of a mercenary group/pirates/et-cetera that hijacks a passenger ship mid-transit? Could be interesting to see where things go from there, especially given that you'd only have to explain character backstories and such through dialogue/internal dialogues/actions, instead of showing all of your cards at once. (Edit: Would we be allowed to replace characters along the way -- perhaps if certain characters go off on entirely different arcs/die? Could add an element of realism.)

Either way, I'm intrigued.