>With a bit more advanced setup, you could even completely cut off the adblock process from accessing any files or any other resources related to the browser, further nailing down security.
How would that even work? The adblocking process has full access to whatever's being passed through it, and therefore it can eavesdrop or tamper (eg. inject malicious js) with the contents.
>Sure, it is possible to have similar (or equivalent) setup for browser plugins, but it requires some special engineering done in the browser - and in that scenario no other apps benefit from the protection. Let's not forget there's much more crucial HTTP user agents than just the browser.
Sounds useful, but it's a lot like dns based adblockers or hosts file, only worse because it only works locally, and only for applications that support/respect the proxy settings.