What about a whitelist? I might just be interested in only having certain sites, like this one or Reddit, translated into my target language. That way I can be certain it is only turned on for sites that I am OK with sharing browsing history and not be concerned that I might have missed adding something to the blacklist.
This is a great idea. Specifically, I want this enabled when I'm wasting time but not when I'm working. So I'd like it to be enabled only on X.com. This whitelist+blocklist functionality could be a user-side setting like with Adblockers.