I originally thought a castle but its already been done so i thouht of a theme park instead where you would have multiple mini mansions to explore as well as areas like, bumper carts moving on their own, ferris wheels, caraousel, paratroper ride, pirate ship,

New types of ghosts would be, 1 clown ghost, 2 showman ghost, 3 food and beverage ghost, 4 ticket ghost, 5 a new pirate ghost more like blackbeard instead of the shark 6

King boo is captured by the showman ghost the one who is in charge

And all the boos are being forced to work in the new theme park. the showman ghost (who is in charge) lures luigi there with the promise of only the bravest of heroes can take on these theme park