Interspecies relationships have happened, so this is not an outlandish idea. So what would people think of a subplot where some girl thinks Ax's Human morph is hot. So they hit it off at one of those dances, and he starts hanging out with her more and more. After finding out she isn't a controller, that is. How well do you think Ax would hide his identity? What kind of girl do you think would fit Ax best?
I would think someone with a good sense of humor, and possibly laid back attitude. If they made her an important character, I'd try to make her different from Rachel and Cassie, so there would be variety. Like someone who's afraid of bugs, and doesn't care for animals very much.