This should've been in at release, it's a simple feature. We have to spend the entire game looking at our character's faces (unless you hide it under a helmet) so we should be able to customize it whenever we want.
I like changing my character's hairstyles alot, and from a RP point of view I wanted my character to start without a beard, then add more facial hair as time goes on, but alas it's not possible.
The "Barber Shop" should give us the option to change Hairstyle, Hair Colour, Beard, Eye Colour, Scars/Tatoos/Markings and Complexion.
Then a plastic surgeon for everything else (Head, Body, Skin Colour)