See the problem with that is, Shinzon was supposed to be Picard's Khan and Khan had for more straight forward reasons for hating Kirk compared to the reasons for Shinzon hating Picard and wanting to destroy Earth. Khan is a better villain because we have a better understanding of what drives him and why he hates Kirk. Sure Khan's megalomania gives him a warped perspective and lets him ignored his own fault for his situation, but he does have a right to be upset, Kirk didn't check up on him after banishing him to that planet and Khan's wife dying would certainly make bitter towards Kirk. All of that is far more interesting then the convoluted, yet underdeveloped motives Shinzon had in Nemesis. Convoluted story telling is not good story telling.