So this exists. Mostly SFW, Slimer fetishists.

Ghostbusters fansite Spook Central is on it.

Looking over the photo sets Hustler provided, there will probably be only six sex scenes with these pairings:

• Ghost Librarian & Ray
• Female College Student & Peter
• Dana & Peter
• Janine & Egon & Louis
• 1950s MILF Monster & Winston
• Gozer & ??? (Ghostbusters Gangbang, perhaps)

I like how casually that's on there. "Ghostbusters gangbang, perhaps?" "Oh, why thank you, yes, don't mind if I do."