I get your concerns - this is precisely why we added adaptative subtitles as one of our first features. So people could say: "I'm a beginner, keep 80% of the subtitles in my native language", vs. "I'm a more advanced speaker, let's go ahead and put 100% of the subtitles in English".
That sounds like a great feature. The most frustrating thing about learning languages is that it is so hard to ease into it, and you have to have a relatively solid vocabulary to go beyond canned phrases, but this sounds like it could help with that.
