I agree that this is an unnecessarily complex question in Australia.
However, I think the treatment of a hypothetical accident by the insurance company would be completely different than the treatment by CASA. And CASA seem to be treating accidents differently depending on whether it is RAA or VH registered and amateur built vs factory built and the level of news attention.
I start by ringing the aircraft's insurer (probably QBE or Allianz). I guarantee they will be easier to talk with than CASA.
The other factors (in the event of injury) will be the injured person's life, accident or loss of income insurance and potential legal action by that person or his / her estate. This area may be the worst of it.
And of course tripping getting out of the aeroplane and falling on the ground, or tripping on a tie down on the way to the aeroplane opens a whole new can of worms which may involve the flying school or airports public liability insurance.
Heaven help you if you are a bloke, the passenger is a woman and you are perceived to have touched her in the wrong place while helping her in or out of the aeroplane.
Just don't screw up. And if you do have everything in your wife's name.
There is another thread about fundraising. The ATO have made this area very difficult for charities. In simple terms, any money given to a Charity in exchange for goods & services is not tax deductible. Someone paying a charity $10,000 for a 10 min flight with you is not necessarily entitled to a tax deduction.
The good news is that over the years I have donated many flights at charity auctions and not one of them has ever been claimed. So, there's a fair chance that this question will remain hypothetical for you. Typically they are bought by someone for a mate as a joke and after everyone sobers up they lose interest.