I agree, though this does not seem like something that should be built until the browser is at least usable, which currently they're projecting an alpha release in 2026. By then things might be totally different, so don't architect yourself into a corner with it, but I also wouldn't invest much or any time into it right now. Focus on building good APIs/extension points though, and those will be immensely useful whether for local LLMs, extensions, or anything.