Title. I say, "if such a thing could even happen," because it might be impossible for a specific byte like this to even be created with RNG. Don't quote me on that, I don't actually know lol.
Anyways, what is the chance of finding any given species of Pokemon in the wild as shiny, having perfect 6IVs, AND pokerus? I know the chance of finding a shiny is ~1/4096 and pokerus is something even more ridiculous. I don't even know what the chances for 6IVs would be.