If you'll forgive me for dragging a Fortress happening into the RL-area of the forums, I have a screen-shot here of a battle report where the Soldier Ant Woman Blowgunner is referred to as "It".
(As in: "The Forgotten Beast attacks The Soldier Ant Woman Blowgunner but It jumps away!", but that's nowhere near as entertaining as "The spinning forgotten beast frozen extract[1] laced with Temptednail's[2] antman ichor strikes The Soldier Ant Woman Blowgunner in the head, shattering the chitin!" and, because the FB is setting absolutely everything on fire, both "The Forgotten Beast is caught in a burst of boiling spider venom!" and "The Forgotten Beast is caught in a burst of forgotten beast flame!")
I'm not saying this is correct (probably due to the peculiarity of how Toady had to represent a transfer to mamallian gender types under the non-mamallian caste-based drone/worker/soldier subdivisions of the insect-race-made-humanoid in question, from the raws), but it is an example.
Back to the Real World, I'd personally, I'd use "They". Then, if there was opportunity to edit my output I'd start hearing all the voices in my head of the countless people who have insisted that "They" is not a correct word for a singular use (to a similar degree that I might condemn the usage of phrases like "PIN Number" or "ATM machine" in theirs) and, if I could, re-write the sentence so as to be able to use some other phrasing that neither suffers so directly from genderlessness (or arbitrary gender assignment, typically but not always male, which could be seen as assuming some aspect to the only partly identified individual concerned) nor tries to assign the plural reference that some people abhor so.
Sometimes it takes an awful lot of rephrasing to get a result I'm happy with, but if one has a reputation for pedantry and doesn't wish to be hoist by ones[3] own petard... I know I'm probably going to get caught out by the Pedant's Curse anyway, possibly due to bad or incomplete editing, but I don't want to knowingly leave any low-hanging fruit.
[1] "A towering blob of flame. It has three narrow tails and it has a gaunt appearance. Beware its deadly spittle!"
[2] The SAWB's titular name, acquired when she killed her first FB and became "Friendly". She's dead now, thanks to the above FB, though. But it looks like she injured it in some way.
[3] I know that the possessive of "one", as in the "indefinite personal pronoun", should be ended with Apostrophe-S, but I have this over-riding feeling that it should belong to the set of "irregular possessives" that forgo the apostrophe (and in several cases don't even terminate with an "s"!), i.e.: me, you, him, her, it, them, us => my, your, his, hers, its, their, our, (etc...)