I could see a human going to a cyborg, but my type 4 body Sith changeing to a Twi'lek? I coudl even see where they get aged from using the darkside of the force. I would love a way to add scars or battle damage some how.
The emperor attempted to change bodies several times on the star wars universe; we also have the mind traps and quests in the current universe that indicates that as a possibility. It is completely explainable on game terms (background histories) such advancements.
They should indeed be a cartel market option, or even a ticket to a far OUTER SPACE Clinic Station on the Outer-rim that deal with drastic changes.