I kinda want Luigi's Castle to be a thing now.
Luigi somehow gains proprietary rights to an abandoned castle through some excuse plot mishap. Of course, the castle is cursed, too--beset upon by all kinds of varieties of merciless monsters; the Poltergust alone is not enough to secure the castle.
Luigi has no choice but to turn to a relative expert in castle defense, and beseeches Bowser for tools and tips. With his help, Luigi secures the castle, finds the source of the curse, and destroys it.
"This lava pit, complete with bubbles, is the ultimate form of castle defense. It can guard against anything! . . . apart from uncannily agile plumbers."
"That's-a fine, big bro can visit whenever he wants!"
@OchotonidKnight "ARE YOU GOING TO TRY TO TAKE PEACH BACK?"
"That's my brother's thing, Bowsy, I just need a hand."
"ALL RIGHT, WE COOL, HERE'S HOW YOU HANDLE DRY BONES"