Everyone seems to have latched onto the harness issue in the absence of any evidence thus far. I think this may just be a red herring in that looking at video and pics of the 5 pax, they were all young and all healthy. If anyone is going to extricate themselves from a tight space, under pressure, atleast one of them is. But they didn't. So is the culprit 5 x harness designs?
I therefore shift my attention to:
Cold shock syndrome.
Loose articles in the cabin area - snagging hazards.
Both of these will provide enough time to determine the fatal outcome.
My final observation.
Having flown over 2000hrs on the twin squirrel (where critical switches/levers are in the cockpit roof), I never gave it a 2nd thought that NO-ONE who operates single squirrel's like this one or similar - where critical switches/levers are on the damn floor - actually decided it was wise to put a protective perspex shroud between the pax and the control(s). Mind blowing in retrospect to think there are operators out there who fly 'strangers' in their cab's yet don't consider the ergonomic layout to cater for their type of operation.
There is a word for this - it's called complacency (Never happened before, so won't happen in future brigade).
Safety Management requires: not reactive management, not pro-active management but predictive management if you are to stay ahead of the safety game. Go looking for problems and don't wait for them to come to you.