Scoff, but this has been done, more or less successfully, at least once that I know of. The story:
Pilot departs Gulf of Mexico shore base flying a 206 to change production crews. As he heads out over the marsh, he starts feeling ill and turns around. Feeling sicker, he initiates a forced landing, but loses consciousness. The front seat passenger grabs the controls he can reach while somebody in back holds the pilot up. The 2 active passengers die in the crash, everybody else survives.