My immediate concern with the unhosted model diagram on the page is how do you make sure the data hasn't been tempered with? The web application needs to see it but now the added problem of not knowing if it's legit because the data source is the end user.

Another side idea that comes with this is something like IPFS or even torrent, where bits of the file storage are stored on individual nodes but incapable of meaningful data unless put together with other bits of data from other nodes.

I admit I'm not even sure how bittorrent make sures the other "bits" are valid, would love to know if there is some p2p-storage.js you could drop on your webpage