the neologism and questionable translation

One of the many dillemas that translators come across is how to go about translating words that do not exist in the target language (TL) they are working with. How should these be dealt with? With great caution, obviously, yet how far can one go? Polish is one of those great examples where neologisms crop up all the time. One only has to pick up a text by Gombrowicz (in the original), for example, and realise that there aren't many words that are not neologisms... Well alright, a slight overstatement, but the point rests. Slang, which often is made up of neologisms, is a differing case - cultural bonds expressed in the spoken word are next-to-impossible to 'translate' (in the true sense of the word), and therefore don't count. (They do, but I won't be writing about that now, or anytime soon either). However, a 'standard' neologism (if such a thing exists) should be translatable. And that's the issue. Translatability. Walter Benjamin writes in "The Task of the Translator":

"Translatability is an essential quality of certain works, which is not to say that it is essential that they be translated; it means rather that a specific significance inherent in the original manifests itself in its translatability."

Reading this made me think: if something is translatable, then surely I should be allowed, as a translator, to make something up in English that would reflect the Polish? If I do make up a word (which, unfortunately, I've been doing a lot recently), can I justify its existence, or am I merely abusing my rights as a native speaker of English by making up a word that I think all other speakers of English will understand, whilst at the same time bastardising my own native tongue?

Suggestions, anyone?