You're not likely to find one. My character, Wolf, is an NH-8, because he's old and never thought he needed an upgrade from the NH-7y3 default form of the NH-8. They'd be pretty rare, and since most nekos have no reason not to upgrade, I'd think the only ones you'd find would be shady characters.
With my stance on history, I would say that you shouldn't create a character that is an NH-2 (I believe that was the first, I could be wrong) up to an NH-17, because it'd make your character a bit too special. They likely wouldn't be in the Army either, or they'd have upgraded. Maybe (maybe) you could have an old neko in an independant organization like Nairan or a pirate group, but you should talk that over with Wes.
I wonder what exactly you mean by NPCs. I've said before that once the player has an NPC, it's not an NPC anymore. Non-player character, see? If you mean a GM controlling it, that'd be up to them.