Fraud can occur when a party lies about assets it owns when entering into an agreement, which would be prevented if you had to present proof of ownership for any asset you claim to own? Most ponzi schemes would never happen.
You can own something, accept payment for it, and never actually relinquish ownership. Besides, the blockchain is only proof of ownership of things on the chain. Real world things are not covered at all.
But the rest of your post is pretty silly. How does a secure digital exchange protect against fraud? It doesn't.