Psychosurgery or pharmaceutical intervention to encourage some of the more positive autistic spectrum cognitive traits seems more likely to work than this. We are far from identifying the genetic basis of intelligence or exceptional intelligence, never mind an aspect as specific as rationality.

It's also not clear that it is in someone's self interest to do this. I know you said retroviral genetic engineering, but for now I'll assume that it would only be possible on embryos. In that case, if someone really wanted grand children, it is not clear that making these alterations in her children would be the best way to achieve that goal.