Hi Vic,Sorry for the long delay in answering. I have been in Denver for the last 5 weeks in transition training for the A320. In fact, I'll be writing an article about the differences between Boeing and Airbus from a pilots perspective soon.
As far as your question regarding pilot incapacitation, you are right, it is an often dreamed of senario. In fact we do have a very specific procedure in case of pilot incapacitation, unfortunately for all of the budding Karen Grays (Airport '75 reference) out there it doesn't involve any of the passengers. In fact there has never been an instance at a U.S. airline (I don't have data for foriegn carriers) of both pilots becoming incapacitated at the same time. Therefore our procedures always assumes that we have at least one concious pilot. In addition, on virtually 100% of the flights there are at least one or two deadheading pilots in back. They are the primary resource for the remaining pilot.
I don't think that this as anything to do with insurance as we would also not allow a flight attendant at the controls! It may seem odd to say, but flying a heavy jet and flying a light aircraft are so different that I don't feel that a private pilot would be of much help. Of course if the unthinkable did happen, I suppose being comfortable with the radio and ATC would allow such a person to get guidance on how to get the autopilot on and how to configure for an autoland (if the aircraft is so equipped). Frankly, I think that an autoland would be the only sure bet as far as getting everybody down in one piece. As Dennis Miller says "Of course that's just my opinion, I could be wrong".
Mark