I like the thought of using blockchain as a part of information security. The main goal is to maintain confidentiality while providing accessibility. However PGP is rather old. Are you also asking if we should integrate the complexity of the blockchain to add more security layers to the protocol for making informational or simple contract transactions (not just monetary) more secure?

As of using bitcoin public keys for encryption of messages, it looks rather a bad practice both because of address re-use and lack of key management and no support for fame and mapping keys to real-world persons and entities. Note that implementing such a system on bitcoin would be worse because of dangerous privacy implications.