"The anti-use would be in any sort of cryptographic implementation, since any "entropy" you'd be gaining by using this data as a source of randomness is completely counteracted by the fact that the source is known. Randomness becomes deterministic once the source of the randomness is disclosed and broadcast ... "

In this design, that's true. But Rabin's hyper-encryption is an example of how a strongly secure encryption system can be built using a very high-bandwidth source of public randomness.