Idea for an app that is only used for DMs and focused on privacy:

- A new public key sent to everyone Alice follows

- This key is used by Bob to message Alice from a new key which contains another public key

- Alice's response sent to Bob's new key using a new key contains another public key

TL;DR Each NIP 4 event uses a new key, sends to new key and has another key to get the reply. New tor circuit is used for each event so all events are created using different IP addresses.