If chrome implements WEI and it isn't standardized, you're not going to be knocked off the internet if you use firefox. That's extremely silly.
[1]: Keep in mind that things that aren't standardized include third party cookie behavior, so the behavior that FF and Safari have, that you support, isn't standardized either. If you're fully against browsers implementing nonstandard apis or features, you can't be in support of third party cookie sandboxing at all.