Had this idea a few minutes ago. Why not have a main villain host Halloweentime each year and conjure up the rest of the villains with them? Almost like an icon for each year.Whichever villain chosen would have tributes throughout the park and would take over the castle in some sort of way. For example, if it were hades the moat could be dubbed as the river Styx, if it were the evil queen maybe a large mirror. All usual villains would be included in the festivities, but one villain would kind of be the central theme of the event.