So I will tell you now something that I have been thinking. Some time ago I was thinking that it would be possible to host a git repo in such a way that it can be cloned in a p2p fashion, indexed by a DHT network in a similar way how BitTorrent works.

I think that that this will be even more easy to accomplish for nostr. So here is my idea:
Every client acts like a relay.
Every client can serve the messages it itself has posted.
Every client can optionally serve messages of users that the local user is following.
Messages, hashtags, user data (and maybe other things) are indexed in a DHT network.
Clients use the DHT network to find and download messages of interest directly from other clients that have them
You can also set a persistent device (or maybe pay for a service or someone can offer such a thing for free) that is always online, part of the network and ready to serve your content (if you are for example posting from a mobile device, which obviously cannot be always online).

This is my very rough and inexact idea. Do you think something like this can work?