1) Michael Myers
2) Pennywise
3) Freddy (with 1 glove)
4) Jason
And I'd also add an arena for each of them so people won't be upset about returning characters.
Michael Myers arena would be in front of the Myers house with jack-o-lanterns and a parked car (slam opponent through the windshield) as interactive areas. Stage fatality would be a lot like the MK9 stage fatality where they were held in front of a car only this time they'd be held against the parked car on the street and a speeding police car would crash and burst into flames, a lot like the scene in Halloween 2.
Pennywise arena would be the sewer with the rain pouring in from the gutter in the background, interactive elements would be various junk and debris that have piled up.
Freddy's Boiler Room with interactive elements being pushing the opponents face up against the hot boiler and also breaking a pipe off to hit the opponent with. Stage fatality would be opening the boiler and throwing them into the flames.
Jason's would be Camp Crystal Lake, fighting would be along the bank on one side of the lake while a camp and people by a campfire could be seen on the other side. Interactive elements would be a campfire and a canoe paddle. This stage would have a fatality where you could drag them to the lake, stick their head under and see Jason as a child with his deformed face coming up and pulling the person down.
