I hear you, or course, but still hard to enforce anytime a dive site has a hard bottom deeper than the depth certified.
As an example, my deepest was on the Forest City in Tobermory where I went to the sand @ 150'. The wreck sits on a slope from 60' to 150'. Where the wreck sits on the upper part of the slope, it is perfectly accessible to an AOW diver certified to 100'. How do you stop them going lower? Who was to stop me from going to 150'? Would your club just not allow anyone certified to less than 150' do this wreck?
Yup, that is exactly what we are exploring now! We have the Stolt Dagali (60-130), same issue.
It's a non-trivial problem. Our safety chair is also a local charter boat captain, and he has taken a serious look at what would happen after an incident in terms of insurance and legal exposure. I think that many old time divers and captains just sort of rely on the tradition of the dive boat being a taxi service, and play the odds (even when they don't know what odds they are playing). Chances are, they aren't going to have a death. But what happens - with regard to your liability - if you take an AOW diver to a wreck with a 150 foot hard bottom and they die? Can the attorney hired by the widow make the case that you had a duty to care that you didn't fulfill?
Maybe @Wookie can chime in here - he knows this stuff better than anybody. But this has me concerned. Between the safety chair, and our president (who is an attorney), we have had some thoughtful discussions. It's not at all clear how to proceed. But the idea of "you don't know what you don't know" apparently applies here. If you take someone to a dive site where they can dive beyond their certification, apparently not all of the liability for an accident can be placed on the diver, in a court of law.
I think that lots of people here will just say that a diver is responsible for their own safety and that's it. But I think that's becoming a false assumption over time. These aren't the 90s. Not saying that I know the answer, but if you are actually running a dive operation as a club, shop or boat captain, take some time to figure this out, and speak with your insurance carrier.