Opera Mini did (and apparently still does) that.

IIRC the proxy server does way more than just compress assets, it re-encodes the page to an internal binary markup format, and handles restricted JS execution with a simplified interaction model (the client had all of 4 events: unload, submit, click, and change, these events would trigger a server call which executes the corresponding handler and sends the updates back).

Not everything worked on that thing (most obviously the complex web applications which were starting to crop up around that time), but it was absolutely magic on unreliable GPRS connections 15 years ago.