@technomancy I suspect the boring answer is it's a little challenging because they want to prevent even loading any code from the ad networks at all. And nowadays the ad boxes are often dynamically created at runtime by client side JS that was already blocked.
Back in the days when web ads were <a href="http://example.org/buystuff"><img src="advert.jpg" alt="Buy stuff" /></a> this would have been a lot easier and I think some ad blockers may have even done exactly this. But perhaps with kitten pics instead.
@vfrmedia sure
Replacing the ads with kittens instead of simply deleting them is whimsical rather than practical ☺️
@technomancy that's kind of brilliant because ads are looked for by the site, to make sure they are not being blocked and that they are rendered
In which case you could do a number of Javascript or sandboxing tricks to let the ad through but, as slyly as possible, alter it in ways that the final rendering is different, not removed