Most of the ideas to change a face or hair are a stylist and they pay gold, right? Well, I have a different solution. You HAVE to chose what you want to look like at begining, so it would be wize to chose a look you like. but if you change your mind, you can buy a Beauty Station. It will be a lot like crafting. Each hairstyle, color, or face will require certain reagents and when you get enough, you can make the magic potion to put on your head and change it. That way, it will have a chalange, but also fufill peoples needs.
Sorry, but that doesn't fix why one of these shops doesn't exist already: identity theft.
As an example for those who don't understand what I mean, let's say that you have two friends, both are male and named Blake Emeraldeyes. They have different facial features and maybe different hair. One could easily buy clothes to match the other and put them on. Facial features would then be the only way that you could tell the two apart. If you had a shop to change your facial features (for any price) one could dress up like the other and change his facial features to match the others. How could you tell who's who?
It is a good idea, But think of it... even if there is an identity theft, other games pull this off all the time! Some of those are Family games too, "Fiesta Online" has somthing called beauty shop that is split into 3 parts, Basic, Special, And Premium. Each one has a few Hair, Face, and Color's in them. Your idea is great, but i'm afraid it will just end up as a special ticket in the crown shop, that wouldnt be good. This is somthing alot of free players want too! Good idea though!