14. It's always possible, there's already a lot of characters whose hair actually has plot behind it. (Ichigo's coloring, Orihime's coloring and hairstyle (twice), Kenpachi's bells.) In fact, Ukitake's hair already has some plot -- it was black before he contracted tuberculosis, but it turned white in a short while after he got it, I think.

But I'd also point out that long hair may be indicative of nobility: take Byakuya, for example, who is so painfully practical that it's hard for him to act like a human. XD And his hair is long, albeit not as long as Ukitake's. But Ukitake is also largely confined because of his illness, so... I don't know, I don't find it terribly OOC, personally.