... the issue is the cabin on the SP series is small and cramped for the passengers being carried on the North Sea. ... ...the perception of being dangerous and is causing a problem amongst the passengers.
I hear you SASless. We might wonder if AirbusH/EC will make EC225 Mk2 with a taller cabin. Not entirely straightforward. For all the tales of Pumas in the back of Transalls, it's the SP that has the normal cabin height and not the S-92.
The AW189 will be the same, as will the EC175, though both will be blessed with monster escape windows.
Add to that the stability on floats that is inevitably better with a lower aircraft.
Let me see now. Do I want a perception of space and comfort or do I want monster windows and stability on floats? I'll take the latter.
EC175 window: see page 9.
http://www.eurocopter.com/site/docs_...&Gas112011.pdf
Once you get beyond about a dozen pax, I think the escape situation is inevitably more complex and the space required for each person may need to rise. Headroom certainly has some value in that regard but I suggest it is not as valuable as floor-space.
I would be delighted if we could see a detailed study of what happens in the back. A bunch of fresh-thinking PhD types getting together with accident survivors and established aviation evacuation specialists might bring us substantial value.