Hyperoxia, or oxygen toxicity, only occurs when you're breathing high concentrations of oxygen at NORMAL atmospheric pressure. If you have vastly reduced atmospheric pressure but a higher oxygen concentration, you'll be fine. 10% of atmospheric pressure combined with near-100% oxygen will do just fine.
Which makes me wonder. You can colonize TITAN in the Sol system straight off, but why not Mars or Luna? I mean, they have no oxygen, but why can't you use your infrastructure to establish a bubble colony? You don't need a world to be suitable at all to establish a colony on it. I don't see the point of having "uninhabitable" worlds, unless they're gas giants. As long as you can get a small part of the place set up to human standards, people can live there. Infrastructure should represent this, meaning that with enough infrastructure you should be able to colonize any world save for ones without solid surfaces or ridicoulously out of human temperature or pressure extremes.
For most uninhabital bodies the problem is gravity, not the atmosphere and not even the temperature (for that reason I usually up the gravitic tolerance for my race to 65%, I realy want to put some people on Mars)
I don´t see a lot of problems with people living on low gravity worlds. The trouble will start when you move them back to earth (bones containing little calcium will not fare well, once back in normal gravity). For Aurora, a race is a race, no differnce between humans on Earth, Mars, or Ceres.
At least that´s my take on it
