Eye color would make the most sense to add to the Aesthetician because choosing an eye color can feel limiting to what hair colors look decent on your character and would be easily explainable by contact lenses.

It would be harder to justify anything else without being forced to call the Aesthetician a plastic surgeon.

My advice to anyone thinking about taking the leap for a fantasia is to just make a junk character on a low-pop server and play around with them for a while. You'll be able to hear all of their voice clips and have complete control over lighting and motion. I think even the most basic subscription is allowed 8 characters and you can always delete them when you're done. Just make sure you pick a tank or a physical dps so you can actually hear their battle voices.