If you could though, if you had a clear understanding of how Trait A and cluster of genes/epigenetic factors Z were related... then what traits would be valued? Some would want attractive, intelligent offspring. After a while though, I wonder if people would really want that?
If you're the kind of person who wants to control the development of your kid's moral/religious/political/etc. views (and lots of people do) then you're not going to get what you want out of that. You might want to select for traits that are just... like you.