So I integrated a page cache (based on KeyCDN Cache Enabler) in Autoptimize, just to see how easy (or difficult) it would be. Turns out it was pretty easy, mostly because Cache Enabler (based on Cachify, which was very popular in Germany until the developer abandoned Cachify) is well-written, simple and efficient. :-)
No plans to release this though. Or do you think I should?