Thats a very academic and static view of content - I don't see how that would work in todays hyper-dynamic environment, where the Ads that are displayed on a site are priced by millisecond real-time auctions before they are delivered to the user, and websites are single-page apps with REST APIs in the background. How would that work?
By transclusion. You'd cache the big, reusable chunks of content, and serve up a fresh transient little document that transcluded both the larger content chunks and the dynamically-included advertisements.