I think it is harder than that.
I think that advanced advert-handling will defeat the kind of ad-blocking that you describe, and by "defeat" I mean that if you don't see the ads then you don't see the web page content either. I get that at The Register sometimes, or I used to, not by blocking but I think when I loaded several pages at once and that either means ads arrive too late or it's just Not Allowed. I reload the scolding news page and it usually comes up fine.
Another model uses a proxy server on the PC itself, which just refuses to download adverts from known advert sources. Or, I'm not sure this existed, but it doesn't download advert-sized graphics to the browser, but to read the picture size, the graphic file has to be downloaded to the proxy server - which is your proposition.
Another Opera product has or is basically a proxy browser; the browser runs in the cloud (not called that at the time, I think) and on your PC or phone (I think the target was phones with low bandwidth) there is something like "remote desktop" so that you see what the browser is displaying. That theoretically could prevent showing adverts to the user although they were present in the browser. But I don't know if it did. It is cheating, after all.
But - it can be done.
I think that a browser with a "reading mode" - discarding junk from a web page and showing you the useful stuff - also amounts to doing something like that.