A comment was made about testing with 332 dunker (if it existed) with 19 people in a more realistic situation. From my experiences in the normal HUET, there is no way this extreme could be allowed from the HSE standpoint. It would be very dangerous and even in controlled conditions I strongly suspect would lead to injury to the testers. I guess this does not say too much about a real heli full of people and the likelyhood of escape.
I think this is work that needs to be done, and looked at very thoroughly, but as a piece of research and not routinely for the general offshore population. Using genuine offshore workers would be a good idea and getting a few dozen dive-qualified ones might not be too hard. Stick bottles on their rebreathers for back-up and you've solved the safety problem.
You need an aircraft sized dunker with movable seats and exchangeable side panels for 332/225/92 ... .
If somebody built this then it could also be a tool for investiging accidents.