Next phase would be to do diffs between the JPEGs and if the diff is smaller than the next JPEG, only send the (gzipped) diff and reconstruct the next JPEG on the client side.

TBH, the obsession with standards is kind of nutty. It's not that hard to implement custom solutions that are better adapted to specific problems. Standards make sense when you want maximum interoperability but not everything requires this degree of interoperability these days. It's not such hassle to just provide a lightweight client in those cases.

For example, it's not ideal to use HTTP2 server push for realtime chat use cases. It was primarily intended for file push to avoid round-trip latency but HTTP is such a powerful and widespread protocol that people feel the need to use it for everything.