Nostr is pretty far along and already well committed to the whole "every user is not a relay" paradigm. Which is fine, it's probably "decentralized enough". One of the key pressure points coming up is going to be the cost of hosting media for relays and the tendency for relays to centralize a bit as the average relay hosting cost increases due to increased users and particularly increased media. If we integrate a P2P way to store and to distribute media now, we can avoid much of that.

For example, we have a NIP for associating a pubkey with a LNURL (lightning address). We can also have a NIP for defining a link to an "external media" which is downloaded via Freenet, Hyphanet, IPFS, etc. Let the client do the work of downloading and re-sharing media content while the relays are responsible for text and links to media. At least for Freenet, you talk to it via your web browser via a localhost port. So a nostr client can easily make links to, upload, and download through it without ever needing to leave the browser. The only thing that needs to be true for that to work is for the user to run the freenet client in the background. Unfortunately, they don't have a client for Android or iPhone, but proxy services (like currently used for media) can help with that. IPFS may be another route, I am less familiar with it. 

If you're doing nostr dev, this could be something that I think would be on the easier side to implement. I'd gladly contribute to a bounties for it, this is something I'm passionate about.