Actually, I have to disagree there. All they needed to do to market SS2 was talk about how the player is alone in a huge spaceship against zombies, with a hawt, mad and evil robot woman out to get him, and throw a bunch of Alien references in. Add the shooter 2.0 buzzword Levine was so fond of using for Bioshock, and we'd have a marketing winner.
No, the engine isn't easily configurable, plus I think Irrational has already stated they wouldn't release an editor.