A way for players to "illegally" change their identity to escape the police, harder to find those same players again.
To be a surgeon that does surgery illegally they would have to be in crime and their client would also have to be a criminal. The surgeon would have past files of all the illegal surgeries they've done, so if they are caught their past clients are also caught.
Give character customization more strict boundaries for this concept to work, such as having to pay for plastic surgery if you want to change your physical body (not haircuts or changing character body weight) just like the real world but your character has a medical record of what you looked like previously so the police can track you. While doing it "illegally" you do not have that medical record.
This would also make "plastic surgeon" a career. Implement it by having players to actually pay for some kind of schooling. Not as long as a 8 year course but a way to limit the amount of players wanting this career; for example it should take at least 1 year and you'd have to pay a lot of in game money.
Have a "surgeon" NPC already in game that players can go to so they can change their bodies if needed. When there are "surgeons" in the game just disable the NPC from being able to change a players appearance and have players look for other players that are surgeons. Such as going to a shop that does surgery.
This would be interesting because it means Police could access medical files to see if a criminal has changed their appearance if done legally.