here is an idea: take the power away from google and browsers and let's go back to a desktop/native solution of intercepting all network traffic. Browsers can't resist that, because corporate networks need to do TLS inspection (sometimes, they are legally required to do so).
Another idea is, for the filtering system to operate a shadow DOM or an entire browser (like a selenium driver) that renders everything unfiltered. But the browser the user is using only sees filtered content. That way, it would become significantly more difficult for advertisers to detect the AD is being blocked. This could be done in a local sandbox and optionally in a cloud sandbox. Outbound network requests from the user facing browser can be blocked or filtered.
Or, just use Firefox. but I doubt Mozilla can resist doing the same thing, given the anti-trust issues Google is facing.