I certainly don't believe that the current Loganair operation is dangerous and wonder what a second pilot would do to remain awake on an Islander.
I guess he/she would participate fully in the operation of the aeroplane and share the workload, enhanceing flight safety - just as they do on all other 2-pilot aeroplanes.
If you have flown an aeroplane of the Islander class with 1 pilot and with 2 you soon realise how much lighter your wokload is with the second brain/set of eyes and hands on board.