I think it already is; if you can isolate the factors involved with generally high intelligence, along with a life style were that person can thrive, you could have a very successful person "designed" by a scientist. But I think that it would be less of a "designed" genius, and more giving them genetic abilities, and environment to succeed in; and you do need both if you wanted to have a living proof of concept. (A genius who never puts in the effort to succeed, won't be a genius.)