OK, Mr AC, care to explain how you plan to cache SSL-encrypted objects? All your caching proxy sees is the "connect me securely to server X" request - after that, it's encrypted and your proxy cannot tell what's being loaded. Worse, since SSL inflates the data sizes of whatever you've requested, your images are up to 50% more data, and your (already compressed with gzip) HTML, CSS, JS etc is the same. So you've added 50% to your traffic for ... potentially nothing.
Seriously, what do you gain (actual, measurable improvements) from switching from http://www.comics.com/garfield... to https://www.comics.com/garfiel...? Nothing but overhead.
And that's leaving aside the fact that SSL no longer guarantees the source server (too many options for MITM server certificate hacks) or security (POODLE etc).
No, make no mistake, this is Google throwing its weight around, screw anybody who doesn't want or need a certificate for their site, or has made a conscious decision NOT to use SSL (not to mention all the corporates with proxies that inspect for malware - now you're mandating SSL MITM by the organisation, or you have a channel for malware into any system).