This is really neat! It echoes many of the ideas we've been exploring with the Webstrates project (https://webstrates.net). We've been using the DOM as persistence layer for building malleable collaborative software for smaller groups, whereas hyperclay focuses on using the same mechanisms for traditional webpages. Recently, I have been experimenting with a local-first approach to Webstrates (https://github.com/Webstrates/MyWebstrates). Might be interesting to explore if a Webworker-based approach like in MyWebstrates could be used for offline editing in hyperclay.