mainly because the airship is a pretty damn big single point of failure
How so? I assume the envelope would be divided into separate cells and the pressures and temperatures involved mean that the actual pressure difference between inside and outside the envelope is basically nill. In other words, if something springs a leak you'll have quit a bit of time to get it repaired, your lifting gas will escape at the rate of diffusion.
they'll effectively be cooped up inside of the craft the same as if they're traversing open space.
Except the craft can be much, much more capable because the environment is much friendlier to human life than open space. Given enough power, you could even work towards pulling breathing (and lifting for that matter) gasses and water out of the atmosphere, not directly but by processing the CO2 and acids.