"I always thought after the Bourketown king air ghost flight, if someone's garbling on the wireless everyone should be yelling put your oxygen on now. Reckon it'd help?" It certainly couldn't hurt in my opinion & to a small degree, I'm a little surprised ATC don't have procedures for something like that following the "Ghost Flight" accident in 2000 & the VH-TAM incident where both pilots were making unusual statements (including garbling or slurred speech).
When I first flew the C441 Conquest back in 1989, the guy that did my training said the two new things that will "bite" for flight above 10000ft are ice & hypoxia. Unfortunately he is/was 100% correct...
ps yes, Helios 522 was the B737 pressurisation accident...