Out of curiosity and maybe this can help, can the input and output be in typical Latin letters that English (and other languages) use, but the language it'self be different? Which is to say, using the phonetics of the other language, but with Latin letters.
I ask because I tried testing this once several releases ago, and it seemed to work fine. Though it was a very brief test, I asked an NPC to talk in Russian, but without Cyrillic and the translation seemed good. (using google)