Ballyheck - why not have CVR in a single crew aircraft. Take Egyptair 763 crash in the USA a few years ago. Although a multiple crew aircraft, the CVR picked up critical information from the pilot who was ALONE in the aircraft cockpit at the time, and who is "reputed" to have nosedived the aircraft into the sea.
I am not a pilot, but doesn't it make sense to have a CVR on all commercial or passenger carrying aircraft?
Surely any mis-communications between cockpit and ground would also be identified on later playback?
Excuse my naivety.........maybe I am talking bollocks but this is logic as I see it.