I don't think that BIP70 is the answer to all these issues. What if I don't want to tie my address to my identity? I cannot use Bitcoin? I believe this would defeat one of the purposes for which Bitcoin was created.
I believe things start to be interesting if you consider your devices identity instead of your identity, and establish trust relationships between devices.
I agree that this is an interesting valid use-case. Still, I think that non-BIP70 transactions are a valid use-case for bitcoin as well.