Great idea, i definitely encourage such a feature.
It actually makes it more realistic as an rpg, as time progresses and events change, look of a character should also change to reflect that. Not to mention people who just plain get bored of their look and really like a change.

Also on that topic, I think we really need more customizations added as well. Much more hairstyles and colors and facial features.
As it stands now, we have too many similar appearances all over the game. Would be much nicer to have the ability to make a char completely unique and that can only be done through deep customization. It would be cool for eg. to be able to do a samurai hairstyle to suit the job when it comes. Many games offer deep customization, this is especially important for an mmo to give each player a sense of uniqueness and identity.