Does anyone else wish all these smarts people bake into per-browser plugins... could instead be part of a localhost proxy?
Then the browser-plugin component could be entirely optional, just a more-convenient way to command the proxy (via some HTTP call that it recognizes and intercepts) to block a given URL or pattern.
As someone who's used a local filtering proxy (Proxomitron) and multiple browsers for a long time, I completely agree - browsers are getting more and more complex and it's difficult to use a plugin to block things that would have been fetched and loaded already by it. The fact that it works for all browsers on the system, and applications that incidentally include non-configurable browsers, is also nice.
On the other hand page modification that involves DOM manipulation/JS interactions would definitely be better handled in a browser plugin, since a proxy is more of a streaming filter device.
SSL is a bit of a pain (especially certificate pinning) since this is essentially a "benevolent MITM attack" but there are workarounds for it.
The warning dialogs do not display if you add the authority certificate used by the proxy to your trust store, and the proxy properly re-signs everything.
That may indeed be a problem. Could use an out-of-browser gui, or possibly configure your browser to trust your own CA as a CA capable of EV somehow, and stick your own EV id in the generated certificate. I dont think this is configurable in most common browsers at the moment, though.
Then the browser-plugin component could be entirely optional, just a more-convenient way to command the proxy (via some HTTP call that it recognizes and intercepts) to block a given URL or pattern.