I don't want to run Firefly or Alien in The Sprawl, but I wouldn't mind my PCs heading up a space elevator for a mission, like Case and Co. in Neuromancer, or the last episode of Cyber City OEDO.
I read somewhere that flechette weapons were really designed for space, because they can kill without catastrophically compromising a space habitat. So the rules reflect that. I also wanted decompression to be orthogonal to winning or losing a fight. You can win and still have your AP rounds pass through your enemy and hit a silk flexiwall just wrong.
When you shoot people in a space habitat using non-flechette weapons or ammo, roll + the number of people you shoot. Add +2 for a breaching weapon, +2 for explosive or airburst ammo, +1 for AP ammo.
10+ Catastrophic decompression event. Nearby pressure bulkheads fling themselves shut to isolate the damage, as atmo fires itself (and any loose contents) out into the void.
7-9 Slow leak. You're going to need to a suit, a leak seal kit, a route away from the area, or some combination of the above, and very soon.
6- It's all good.
Anyway, I feel the breach/explosive/airburst/AP is maybe a bit too fiddly. At the same time, I don't want those things to automatically cause problems. Will try to run this sometime and see. I also need to come up with decompression rules. Act Under Pressure seems like a good enough fit in most ways.
In the spirit of being a fan of your edge runners, they'd probably know going up to space that regular weapons are extremely dangerous to use inside a space hab. Unless they're already wearing pressure suits...