I think, in all fairness to CCA, that he/she made a 'slip of the keyboard', and was referring to GASEOUS Oxygen systems, i.e. bottled Oxygen.
It was always my reasoning, and my course of action on the one occasion that it did happen to me, to descend immediately to 25,000 feet. Range will suffer, and diversion to an ERA may be necessary, but operating anywhere above 25,000 feet without oxygen availability is unacceptable.
If MEA or Grid MORA was significantly above 10,000 feet, then an immediate route change would have to be added to the descent to 25,000 feet.
At 25,000 feet, time of useful consciousness (TUC) is 4 minutes, and, if operating an aircraft with an emergency descent capability of 6,000 to 7,000 feet per minute, one could be safely assured of descent to 10,000 feet in less than 3 of those 4 minutes.
Having descended to 25,000 feet, and made a route change if necessary, the fuel situation can then be re-evaluated to ascertain whether an En-Route or Off-Route Diversion is justified or required.
What does intrigue me in reading CCA's post is the consideration for operation where no ERA was available. Doesn't your Regulatory Authority and/or your Company's Operating Policy require that the aircraft must carry sufficient fuel to divert to at least an adequate airport following decompression at ANY phase of flight? (Not an ETOPS consideration, it applies to all aircraft).
Regards,
Old Smokey