This doesn't necessarily have to be a Vs. type movie, Pinhead & Michael Myers I mean. They could easily do a crossover where Myers found the box as a kid and released Pinhead, who saw the makings of a real evil so pure that he just couldn't waste it on sending Myers to hell or making him into another cenobite. Hence the mass murders, hence the invincibility of Myers, and so on. The ending could culminate with a confrontation or a battle of some sort between the two, but they could easily avoid the stigma of this being a "Vs." movie if they wrote it correctly, and I for one would definitely pay to see it.