If my wallet would be big enough I would take the insurance if it existed and only costed a small percentages of what I have.
The only problem is, how would the insurance company verify if you indeed lose your wallet?
How could they see if the amount you take the insurance for is really the amount you own?
I could take an insurance for 100.000BTC and than claim I lost my wallet.
How would you verify that this is true and not that I had only 50BTC at the moment I lost my wallet, or that I even lost it.
I imagine a copy of your wallet would be stored in their vault and would therefore lessen your premium....
That would be, in effect, no different than gold storage fees. Cheaper, sure, but ultimately, you would be paying to maintain their infrastructure for off-site backup of your wallet. That would be the cheapest service. It would also be the least secure. So, a real insurance plan like you originally suggested would be a premium on your ability to maintain your own wallet. Those premiums would be higher but more secure/anonymous.
Ta,