while this seems unlikely, I am new here and believe that MP would not take from the gameplay. The only problem I can see would be if one person knows more than the person they are playing with, they would ruin the shock of a certain part for the newer guy. I think that MP would work great in terms of all the custom games that are around.
I recognize this however : It is never going to happen.
What I recommend : Play the game in a dark room with your speakers turned up with a few friends, it is WAY more fun, and not to mention the communal aspect of fear just amps up the fear factor exponentially. Big fun with friends