You can't, but that is irrelevant if the centralized service is required. You can point at the blockchain data all you like, but if the centralized service that

You can't, but that is irrelevant if the centralized service is required. You can point at the blockchain data all you like, but if the centralized service that you rely on chooses to ignore the blockchain data, you're out of luck. Hence, you either need no centralized points, or just ditch the blockchain and put all your faith in the central resource. If it is trustworthy, great, everything has become much more efficient. If it isn't, you're screwed, regardless of whether or not there's a blockchain.