I’ve put some thought into this. The biggest roadblock to P2P is 24/7 persistence. You have to be online.

I think the most straightforward path to this is having the ability to setup a mailbox sort of how the relay works but on a machine that’s on a 24/7 stable connection. Because it’s already cross compatible with Linux systems, it would make the most sense to have a dedicated mailbox there, and have it forward your messages that were missed while you were offline.

Once the mailbox is set up, it’s just a matter of tieing the separate mailbox identity to forward messages to you once your online. Ideally integrate tors built in authorized client protocol to ensure only one person is authorized to the mailbox.