How could it be good, at least in natures way of things? It may be neat to see exotic species out your backdoor, but not cool at all. This is why many states here in the US have strict laws about what comes into the state itself. Here in AZ, we are not allowed such things as Crocodilians or Snapper turtles. Reason being, feral pests help wipe out the natural habitat and animal species in those ecosysytems. We also have strict laws concerning the native species which exsist here. It is all about the best thing for the naturals of any place.
I would rather be able to see any animal in its natural setting that have them in my home. Feral pests (including cats and dogs!!) IMO should have strict laws (depending on a few factors), even more so than those placed on native species. They after all, they are more damaging than humans in many cases. We wipe out habitat, they (pests) remove the rest.