Explosive decompression/auto descent??
Staying away from any speculation on the B737 accident, how hard would it be to engineer a "loss of pressurisation" mode in modern autopilots?
If cabin pressure sensed above (say) 15,000' for more than 60 seconds, or 30,000' for 30 seconds, with no "horn cancel" from pilots, auto squawk 7700, wait 30 seconds, turn off airway, and start auto descent to a safe altitude for the sector.
No need to get bogged down in the details here, just airing the general concept for discussion.