The way I interpretted a section from The Last Wish was that all soceresses eventually have deformaties repaired; things that occurred due to environmental influences could all be fixed. Only the really gifted ones had the power to alter their appearance such as changing their face, body shape or eye color. Here is an except from The Last Wish. For those of you who have access to the same edition that I have, the Orbit paperback with a red cover, it starts on page 302, and I am copying it exactly as written, so please don't bother telling me that you don't need an s after the apostrophe of of a noun ending in s. That is how it's written in the book and I'm just copying it:
Each to their own taste but, in actual fact, not many would describe sorceresses as good-looking. Indeed, all of them came from social circles where the only fate for daughters would be marriage. Who would have thought of condemning their daughter to years of tedious studies and and the tortures of somatic mutations if she could be given away in marriage and advantageously allied? Who wished to have a sorceeress in their family? Despite the respect enjoyed by magicians, a sorceress's family did not benefit from her in the least because by the time the girl had completed her education, nothing tied her to her family anymore-only brotherhood counted, to the exclusion of all else. So only daughters with no chance of finding a husband become sorceresses.
Unlike priests and druidesses, who only unwillingly took ugly or crippled girls, sorcerers took anyone who showed evidence of predisposition. If a child passed the first years of training, magic entered into the equation-straightening and evening out legs, repairing bones which had badly knitted, patching hairlips, removing scars, birthmarks and pox scars. The young sorceress would become attractive because the prestige of her profession demanded it. The result was psuedo-pretty women with the angry and cold eyes of ugly girls. Girls who couldn't forget their ugliness had been covered by the mask of magic only for the prestige of their position.
The first part that sticks out to me is that the list of things typically altered are either poorly healed injuries or environmentally induced defects. It implies to me that if what was hidden under all those deformaties was only somewhat good looking, then that is what they got.
The second part that sticks out to me are these sentences, "not many would describe sorceresses as good looking," and. "The result was psuedo-pretty women." This, to me, reinforces that what gets fixed are only injuries, environmentally induced defects and scars, which could or could not result in a drop-dead gorgeous women based on her genetics.
I think I also recall something in Blood of Elves where they mention that only the most powerful sorceresses can alter their appearance, but even then it is just an illusion and not real body alteration. I don't have the time or interest to search through it right now just to find it.
Ultimately, I think what we have here is something that is very typical in video game development. A developer, mostly composed of men, making women in the game as drop-dead gorgeous as they can because they want to and not because it is what is stated in the text. Even in the first game, there are several areas where it went against canon. So it is not a stretch to assume that they have done the same thing with sorceresses because they wanted some extra eye candy in their game.
And P.S. to GOG, you guys really need to implement a "preview post" function on these forums.