I think first choice is the easiest (as well as what I've, uh, been doing so far) and the various arguments for and against have been laid out well enough.

I do like the idea of being able to switch between a universal language and, say, speaking Japanese. Like, that's the only way Nanoha would actually be able to explain that "Kokoro" means "heart" in Japanese, for instance XD

Barring that, the subtitle idea could be hilarious.