Personally, I would think one of the Ascians. The Warrior of Darkness feels like the opposite representation of our character, which would feel appropriate (to me) if our character was the protagonist in NT (not exactly feasible/practical), however the Ascians represent a primary threat and are sort of a direct opposition to Eorzea and Hydaelyn overall, which while our characters are technically from somewhere on Hydaelyn, we're still sort of the X-Factor where-as Y'shtola is one of Hydaelyn's "native" inhabitants.

Just my two cents. X)