Provided they are operating correctly, the current precautionary systems should provide adequate protection. It makes no difference whether decompression is rapid, or slow and insideous. As cabin altitude reaches 10,000 feet a warning should sound, and at a cabin altitude of 13,000 feet oxygen masks should auto-deploy. Accidents like the golfer's business jet must be the result of cascade failures.
In the Helios incident, speculative reports suggest that the pilots were incapacitated while some at least of the passengers were conscious. Many of the victims recovered from the crash site were reportedly wearing oxygen masks. Among several other possible cascade failure explanations, the one that would best explain why the crew did not initiate a descent would be that they received no warning, failed to don oxygen masks and passed out. If I were to suggest any modification, rather than have a system that overrides both the AFCS and the crew to initiate a descent, it would be to include redundancy into the cabin pressure warning system. Just thinking of the possible failure modes for an auto-descent system makes me tremble...