You could use Risus or Wushu since there's so easy to customize. Sounds fun though. Would this be a one shot or campaign?
The original idea of the steampunk one came to me as the beginning of an Iron Kingdoms campaign. The players would escape their underground dystopia into the world of Iron Kingdoms and now have the choice of going on and startling their lives fresh or perhaps gathering strength for a future return to their home to liberate the others. However, as I sat down to start writing it I realized I had a lot more fun writing about the complex and the thought something this cool was going to play such a bit part in the story seemed like a waste to me. So, the way I have it structured now would be a one or two shot with the first session being about introducing the place to the players while feeding them tidbits which shatter their characters' perceptions about the status quo. The second would be some event which either they've instigated (stirring discontent) and has gotten out of control or an event that happens outside of them which lets the players now that this life all of them they have been living is unsustainable. It then becomes focused around escaping the complex while evading the 'authorities'. If they want to try and convince others to join them, they can, but they know they'll be under the gun and some of the residents are stubborn and remain deluded.
Anyway that's my outline thus far. A lot of the particulars remain to be decided and I'm more than open to suggestions.