> At least on iOS, this is an easily solvable problem on most web sites even without AMP: tap the "Safari Reader" button in the toolbar to get a text-only version of the web site. I assume that something like that is a thing on Android and elsewhere.
I'm not sure it's technically true; the text on the page needs to be loaded, but that doesn't mean every other HTTP request associated with the page has to have completed before Safari makes the Reader button available. While this is entirely anecdotal, I can definitely see that button appearing before pages are fully loaded.
Option one doesn't require downloading all the images backgrounds and and videos and other stuff until it's been determined that that should actually be displayed by reader mode.
You need to load the page first to do that.