Ok. Figuring this needed to be polled because I am curious.
I think N is Zoroark. After playing the game twice over paying attention intently. Proof to me that he Z is based on two things. One) Meeting human in Losthorn Forrest talking about how a pokemon was abandoned there years ago as hes walking away it changes to a Zoroark. Two) Chasing Zoroark to Ns castle, and N all of sudden appears.
Made me think "Wtf"
Other things that made me think it was the Final battle with Black Kyurem. With that story and how N says that he can talk to pokemon and yet no one else can?? Farfetched perhaps, but thats my conclusion. I'm sure story creator wanted you to think about that for a bit without saying anything.