It's not possible for them to easily ad customization features. The problem is the speed of datatranfers on the servers. Yoshi P. spoke about that when it was just about seperating Au'Ra horns form the face.
Every player is a little data package. And when we meet others in game we send and receive a lot of data packages from other players, so that they can be displayed right (race, gender, hair, eyeform, and so on, everything).

If they ad stuff those packages grow very fast immensely and the datafraffic can soon be too much for the servers. That's why they did not add stuff like seperate Au'Ra Horns.

Of course I would love to see more options! But I guess it's just not that easy. Yoshi is no wizard who can make that technical components get faster as they are able to. :')