4. This is something I haven't seen anyone else mention: what if your hair length was dynamic? Say, from one season to the next it would grow somewhat. You could go and get it cut for a semi-negligible amount of gil in the fancy part of town anytime, but to see it longer than it currently is, you had to wait a little while. Eh?
Along those lines maybe something more then just preset hair styles maybe allow us to do some tweaking to its length and other things.