> It's definitely a copyright nightmare - so no clue how this could work.

It could work as a decentralized free and open source system that doesn't care about copyright. Like how torrents work now, but it would be good to have it work over Tor or something. Perhaps as a DAO for the management aspect of it. I don't know how exactly. But disregarding copyright by using a centralized company is the wrong idea.

Or you can do the lawful approach and try to work within the framework of that copyright nightmare. But "fuck copyright" is an easier path.

You - as a company - can just avoid any copyright stuff when your extension saves the stuff only on the client. I see there are many other issues then.

The torrent approach is nice. I could imagine a selfhosted way to store the data (for a group of people)

Tor is a honeypot run my government intel operations. Don't use it.