Breathe (Part 2)
The ideas posed in the first part of this post would be the point where I'd leave things for an Aussie Freeform. A few archetypal ways of manipulating the situation, a few goals that point certain characters in certain directions...then you just let the players go. A GM per 5-10 players (plus a head GM), and if decisions need to be made, the outcome is determined by whatever is best in the context of the overall story, even if things look like they should head a different way at the immediate scale. Maybe throw in some egg timers for specific effects that require delicate work (like hacking the server, tending to someone's wounds, fixing the power, or adjusting the oxygen-beds). Players can't do anything else while the sands in the timer are running through; and if they are disturbed, the count resets. Combat would be enacted through basic wrestling, each player has a literal bottle on them representing their oxygen supply (maybe attached by loop velcro to a hook velcro ...