Also, if you're a distro mantainer, configure apache and nginx defaults to make this is the default behaviour.
Even better: instead of redirecting to any wall of text with a long explanation of the political and technical reasons of this choice, just display a big, loud "ERROR" message stating that their browser is unsupported due to the presence of this module, and a small tutorial on how to deactivate it from the about:config page, if available.
However, I think the other stuff that you had mentioned would be OK.
Furthermore, a distro maintainer could configure clients by default to disable WEI (or to not include client programs that have WEI).