For Ye Weiming, accomplishing this isn't too difficult.
While Ye Weiming doesn't possess the ability to regenerate a severed limb, he certainly has the expertise in limb transplantation, and it's quite extensive!
After all, similar operations like limb transplantation are almost impossible to accomplish under the original medical conditions of the main world. Yet, within the story backdrop of the "Wind and Cloud Secret Realm," this is nothing but a routine procedure.
There is definitely more than one Divine Doctor capable of such feats!
Fortuitously, Ye Weiming received a medical heritage specifically focused on this area from within the "Wind and Cloud Secret Realm." Hence, as long as he can resolve issues like rejection reactions, replacing parts for others falls entirely within his regular business scope.
By comparison, making Yang Guo rejuvenate to look younger than Xiaolongnu seems somewhat more challenging.
