I would have thought this type of human experimentation is already illegal. If not, we need to pass a law. Humans are not tinker toys to be played with by jerks in lab coats.
Mitrochondrial defects, as birth defects, are very rare in people because they are so often fatal even before birth. This technique, of adding mitrochondria, increases the risk of these serious and generally fatal disorders.
There is also the massive legal liability, since couples coming in for designer babies are even more likely to sue for millions for a child born with any defect.