Absolutely essential from my point of view to ensure a good character mix. You don't get Penelope Pureblood signing on for a voyage where she knows she's going to get shot at. However, she will hop on board if she's going to go see her Lilac Lovely, her best friend from college, during some well earned time off. That's the only thing that worries me about a specific kind of merc job--unless you get really well differentiated characters, it becomes too much of the same. That's not to say it can't be done, but the GMs would have to really well regulate character sheets to make sure people were different enough. This isn't to say that it has to be totally clueless people. That could work, but I think you need a couple drivers of the story initially until everyone can get their character on the train. But this doesn't actually have to take place in motion. Think about a bunch of people trapped in a room waiting to be called for jury duty. You're just as likely to have the Special Forces guy who did three tours in Afghanistan as you are to have the office paperpusher. And now I'm beginning to think of this zombie board game that totally lampoons the different types of characters you find in [link=http://tvtropes.org/pmwiki/pmwiki.php/Main/ZombieApocalypse]zombie apocalypse[/link] movies. Not trying to suggest a zombie game here--just saying I'm thinking about a zombie board game I really, really wish I could play right now.