I don't think that will help very much. It might stop a few people from getting dangerous pets, but those that do still have a ticking time bomb on their hands. There will still be attacks. They are still ubstable dogs, due to the long breeding, it's in their genes. A lousy owner will make them worse, but that bred in danger is still there. Having seen the scars left by two attacks to friends, well.............The better idea is to prevent attacks from occuring, not by having some insurance company pay after one happens.
They are not ticking time bombs, they are dogs. They will not attack unless the owner has given up their position as pack leader. As I said before, submissive members of a pack don't even eat unless the leader says they can. All dog attacks, even the biting small dogs, can be attributed to failure of the owner to demonstrate proper pack leadership.