I tend to say "he" because I see V as a male. I don't think any pronoun, invented or not, is wrong with him.

In French, what I've translated so far uses what seems to be the character's opinion (masculine for Roy for instance). The tricky part is that adjectives are also masculine or feminine, so if V says, for instance "I am tired", I have to find a way to rephrase it because otherwise "tired" would be either male or female.

"He" isn't really the word used when the gender isn't known, though. It's used when there is at least one male. Otherwise it depends. Ants, mice, spiders if the gender isn't know (or if they're gender-neutral, for ants) are referred to as female. Cats and dogs as males. Whales as females, dolphins as male. It's linked to the fact that there is no "it" in French, so every animal name has a "gender" even if it's used for the whole species.

"Elf", however, has both a male and a female form ("un elfe" or "une elfe"), so although they're spelled the same, articles and adjectives would still be different, and using the male form would mean V is a male (if V himself was to use it).