No one's asked about adding extra parts? He already looks good as is of course.
The gods probably didn't consider the option of having more parts to remove. Yes?
This does makes me think of one theory, what if the master can only control Asterion's appearance but not his "being"? As in, you could give him wings but they couldn't be functional at all, merely aesthetic. In a sense this can also explain why the master can't just heal Asterion, since you'd be fixing his appearance but his "being" would remain damaged. I don't recall the exact wording of it, so I could be way off.