(I swear, bitcoin is becoming more and more like Cosby talk, with a bippity here and a bippity there...)
I'm thinking of something along similar lines. I am working on providing multisig addresses for escrow transactions. the output of which (to the merchant, all going well) would be going to either a BIP32 deterministic address, or a BIP38.
For what it's worth, I love the fact that BIP38 can support deterministic addresses also. No site should have an online wallet, I beleive their only purpose should be to create the transaction which others sign. Get em off the site and into a two factor offline wallet!