None of the other pregens have Singleton as a rival. If the player roleplaying Singleton does nothing suspicious through the entire scenario, then at the very last moment, when the ship has taken off, decides to do something to kill em all, like crashing the ship (assuming Singleton has a reason to prioritize her agenda over her own mortality), wouldn't it feel like victory was robbed from the other players?
What if instead of gotcha surprises, there is a clue of betrayal in someone else's agenda, or perhaps the introduction of some sort of clue of betrayal midway through the scenario? So that everyone can be clued in to the existence of a traitor(or two). To serve as a foreshadowing device that also ups the ante in terms of paranoia.
How do you guys feel about the traitor mechanic in the scenario?