Walter,
You want to work on an assumption of risk basis, however, not all countries in the world allow legal waivers etc.
In the UK, if I am the more qualified diver, I have a legal duty of care to ANYONE I dive with, and that duty of care can not be waved, like with the PADI waivers. If they screw up, legally I have to help. If I screw up, then not only am I in trouble with potential law suits from parents / relatives, but also from prosecution by the police etc.. if I don't do everything possible to help. I have to help untill my efforts would 'manifestly put my life in grave danger' - ie I have to do everything bar kill myself to help them. This doesn't just apply to the people I am diving with. If I am busy, and don't see other divers having difficulties (nothing to do with me, or the group I am with), then I still have the same duty of care.
I would like to see much better diver education, as I see FAR TOO OFTEN people diving with substandard skills for the conditions they are diving in. However, often they do not have enough knowledge to know that they are a risk to themselves and others. By simply being in the same location as them I have a duty of care to these people as well.
Whilst it might work in the US to say 'he knew the risks... and he signed this waiver' this doesn't work in a lot of countries, where there is a statuatory duty of care.
The PADI style system works well when under US law, but the actual responsibility on DM's and above under other legal systems is much greater. Certainly in the UK, the waivers are about as much use as a chocolate teapot, they at best can be considered as an acknowledgement that they are doing something dangerous.
I think that to change the mentality of a lot of divers needs a completely new approach to diving, however, it is very hard to reconcile a comercially orientated approach with a significant raising of training standards. The idea of scuba police is not a nice one, but, some form of system is needed to allow people to know their experience, dive within it, and gain the relevant experience under guidance untill they are capable of making sensible decisions for themselves.
Some form of 'mentoring' system would do this nicely, but there will always be a significant element that believe in the 'assumption of risk' attitude. Personally I think that perhaps after a period of mentored diving people should be able to take responsibility for themselves, but only when they have experienced enough diving to know what they know, and what they don't know.
Jon T