Besides AdGuard I also have my own extension that loads userscripts from my own server (that uses the new userScripts API), so I think I only see my own point of view and the things that would potentially limit my solutions.

So far I'm able to block everything I want, but I mentioned replacing the response body because this is the only way I could modify or even inspect the service worker.. I think this vector could help circumventing ad blockers, but again - it would only matter if there were ads I'd not be able to block.

When it comes to distribution, firefox sucks because I can't even run my own extensions there, my distro doesn't package firefox developer edition so signatures are required. In contrast, Chrome let's me load unpacked extensions without any problems.