the psak from Outsider’s Rav illustrates a major difficulty in paskening practical halachah. The Rav is undoubtedly correct that it is assur to crossbreed animals. The question is, what constitutes crossbreeding. Everyone agrees that breeding a jack donkey on a horse mare, thereby producing a mule, is assur. What about breeding a Limosin bull on a Holstein cow? Limosin cattle are hardy and disease resistant so their heritable traits are desirable. Here’s a case where the Rav really needs some hands-on (or hands-in) experience.
Secular, what you imagine cannot be done. The animal that has cloven hooves but does not ruminate is the pig. It is impossible to crossbreed any ruminant with a pig nor is it possible to crossbreed two ruminates and end up with a non-ruminant. On second thought, It might be possible with modern genetic engineering and recombinant DNA, but not through the normal, barnyard variety of gentech.