I think Luigi's Mansion was always going to be an uphill battle when they chose to incorporate the ghost house environment/Boos into Mario Kart. Granted, Forbidden Journey presented a similar problem for Potter expansion: They assumed they only had one shot at a Potter dark ride, so they covered a lot of ground that they'd inevitably explore again (dragons, Forbidden Forest, dementors).
I do think a Luigi's Mansion ride would rule, but unfortunately, the ideal ride system for it was... probably what they used for Mario Kart, with the AR goggles. Imagine if you could only "see" the ghosts in AR...