Sharing a BIP47 payment code addresses most of the above shortcomings. However, it introduces the following problems:

• The BIP uses a notification mechanism that relies on publicly known per-recipient notification addresses. If Alice wants to send funds to Bob, she has to use the same notification address that everyone else uses to notify Bob. If Alice is not careful with coin selection, i.e. ensuring that her notification UTXO is not linked to her, she will publicly expose herself as someone who is trying to send funds to Bob and their relationship becomes permanently visible on the blockchain.
• The BIP does not say anything about address types. Receiving wallets therefore have to watch all address types that can be created from a single public key. Even then, a sender could send to a script that a recipient cannot spend from.