That wouldn't address Stallman's objection; regardless of which browser is used, the JavaScript delivered by website operators would still be executed in the user's browser.
I am aware of his objections. I agree that dealing with Javascript is a challenge. But the consequence of that there is no GNU webbrowser and Javascript implementation is, that all users have no real choice but use other browsers which might not even try to protect the user.
Consequently, I consider this as something the GNU project failed to address. Why isn't there an official GNU webbrowser with a reasonable Javascript implementation? One where the browser and the JS engine would be free software and which could be seen as a reasonable platform for a modern web?