The whole genetics project of the Bene Gesserit may have been dubbed a failure because Paul wasn't a girl but there was nothing stopping Paul and Feyd-Ruatha acting on that sexual tension they had in both book and film.
Paul could have taken Feyd as a third Consort. Just imagine Paul with his Empress Irulan and his wife Chani sitting at his side and Feyd just sprawled on the dais steps just wearing something scandalous like
You were right Reverend Mother Gaius Helen Mohiam, wasted potential.