Sure, among the many other benefits of not having to accomodate people onboard and not having to deal with other "human factors".
But after all these decades of making sure pilots can breath, you would think oxygen delivery wouldn't be a problem. If they are all grounded, then there's reason to think the problem occured because of a design/manufacturing/maintenance/procedural fault. And those things may just as well occur with hmm, the flight guidance system of a UAV or how about targeting system. They are built/maintained/flown by humans just as well.
So alone, being able to get rid of this system or risk, not a pro for unmanned imho!
Yes, Shawn, there's that risk, especially with today's "commonality" requirements, striving for an ideal standard on every aircraft fleet-wide. Standards and architecture commonalities are great, but it should mean that if you opt for one aircraft, that you don't need to restrict yourself to one option and have alternates. (ahum, F136!)
Maintaining a mixed fleet of aircraft, even mixed inventory of their systems, is expensive and troublesome, which comes risk as well, and I guess it's opting for the lesser of two evils. Uhm, mostly that means the less expensive one in post-Cold War days. But you can also use the economies of scale to have a better support infrastructure, monitoring/diagnostics, etc. So it doesn't take an accident before the problem is found.