Wingnut writes:

Consider who would have been landing the plane if something had caused
the pilot to also conk out, though. Then her prior flight experience
would have become quite relevant indeed.

Not necessarily. In a situation like that, what would be most important would
be her ability to follow instructions precisely, and the availability of a
qualified pilot to guide her over the radio. These two things would override
any piloting experience she might have.

There are two myths that need to be dispelled, namely (1) the notion that
anyone with any piloting experience necessarily will do a better job of
getting an plane home safely in an emergency, and (2) the notion that someone
without any piloting experience would necessarily crash the airplane.

The skill needed when both pilots get sick from the fish is an ability to do
as one is told, and this is independent of piloting experience. Additionally,
a qualified pilot needs to be available on the radio (preferably an
instructor). An experienced Cessna pilot without help over the radio will
probably get in some possibly fatal trouble, and conversely a non-pilot with
expert help over the radio may well be able to land the airplane safely.

This has a great deal to do with automation and the differences between
airliners and small aircraft.

You would definitely want to avoid someone who might be tempted to take
initiatives rather than just follow instructions--and for this reason, putting
a Cessna pilot in the left seat might actually be a worse idea than putting a
complete non-pilot in that seat. The non-pilot might be more likely to just do
as he is told, which is exactly what you need.