The practice of illegal clone brain transplants figures in some of the Vorkosigan series books: The clone-children of various customers are raised in cohorts, and taught little while enduring years of strictly controlled diets, cosmetic surgeries, and exercise regimes.

Then, one day, the are told their important and distant "parents" are finally arriving to bring them away to their new life...

Anyway, the point is that any aging wealthy pedicidal murderers are also gonna insist the body is perfect before they move in, meaning some other brain is going to be doing the work.