Wettek, just in case you do come back to the Board I thought I'd add something to your thought process.
First, your focus seems to have shifted from your original post where you seemed to be concerned about your liability and insurance company to your customers relationship to theirs.
While, it is good to be helpful to others that can be taken too far. Heaven knows I welcome the friendly suggestion, or the helpful hand when I need it. That is what good people do for each other. But your approach smacks more of paternalism than anything else. That is not welcome by me or most others.
Second, my insurance company, and I dare say most others, could care less what I tell you or anyone else in your situation. My medical or life insurance contract is with them, not with you. There are specific provisions in the insurance policy about prexisting conditions whether the insured knows about them or not. There are also specific provisions about uninsured activity. None of those provisions care a whit about what the insured tells you.
So, in light of what you've posted about Australian polices and the well publicized diver abandonments on your reefs I'm going to have to think long and hard before bringing any of my tourist dollars to your country. (To clarify: This comment is to illustrate that there are economic consequences to imposed policies, no matter what the intent.)