In Dutch, like in German, we write compound words without a space, so you can also invent completely "new" words. If I enter such words in Google Translate most of them are correctly translated to English and French. Granted, splitting a word into its compound parts (= several existing words with maybe an "s", "e", or "en" between them for easier pronunciation) is easier than having a base word + inflection + changes for pronunciation, but it shouldn't be impossible for an AI to do this. I do think you'll probably need custom rules or extra information per language, corresponding roughly to some grammatical rules or patterns.