Hello!
I totally agree with this feature, these would be my reasons and ideas:

- Hair color and hair style are the easiest things to change about your appearance, why wouldn't it be same in a virtual game?
- Having a local barber would be an easy way to accomplish this, increasing game immersion;
- It would be a good gil sink, the game economy sure needs it;
- And it would make people really happy, giving them more control over their character.

Full re-customization isn't a bad idea and i support it, although it can break character identity. Still, it is vital to feel that you have control over your avatar in a video game, especially in a MMORPG in which progress is slower and the bond stronger. One way of achieving this is to be able to change your appearance once in a while to keep players from getting bored.

Example: After three days of fishing you might want to reflect that your character got a tan
Your character would look even more fierce as a marauder with facial hair and scars.

Having a limited number of do overs per year, along with a fee could be efficient ways to limit it.