In a poem everything matters. The sound of words, typography, etymology. A grammatical category that might be inert in a non-poetic use of language comes alive in a poem. (By inert, mean that it is grammatically functional, but essentially meaningless.) Take the example of gender: a noun can have a grammatical gender, but that gender is essentially meaningless in everyday language, where we don't think of "el sol" as male in any but the grammatical sense. But in a poem, the gender signifies maleness. The sun is male, not just grammatically "masculine."
My idea for translation (one of my ideas) is that in a translation of a poem, everything should matter, just as it did in the original. By this I don't mean that it should matter in the same way, but rather that it should have that same feeling of necessity. I should think of the etymology of word, even if it is a different etymology than that of the corresponding word in the original text.
This is a roundabout way of saying that the translation should be a poem. You know it's not a poem when the translator starts justifying questionable choices with reference to the original text.