Firestorm, I believe that in your Cheeseburger In Paradise review, you accidentally stumbled upon something brilliant. Would you consider writing a screenplay in which Scooby Doo and Shaggy come to Omaha and go on a wacky adventure with you?
Yes, and I just got to think of a Villain or Villains because The great Scooby Doo on zombie island animated movie had multiple credible villains, and kind of seems borrowing from the Wicker Man in a obvious way.
I'm guessing you just want those 2 characters of the Scooby gang, and I know me.
I don't recall a Scooby Doo movie using a slasher movie a possibity whether supernatural, or ordinary.
The ghost of H H Holmes the infamous brutal murderer, or the ghost of Jack the Terrifier the infamous uncaught brutal murderer best known Jack The Ripper.
He was never called Jack the Terrifier but since it's a fictional story it be done for something creative, also sensible because he's a brutal murderer add in a ghost is a Nightmare on elm Street or Shocker style Horror.
Terrifying Jack aka Jack the Terrifier, Jack the Ripper could be the right hand man of the Main Villain.
A main Villain that would be a new character.