Yeah, now that Curse of DarKastle's building has been allocated to a coaster, I firmly believe the Killarney Sim Building needs to be utilized for something at least darkride adjacent—whether it be a new simulator, a flying theater, a madhouse, some sort of new theater attraction like Danse Macabre, one of those new compact, turntable darkride concepts, or even a themed, indoor flat ride.
Long-term, I'm in favor of a coaster utilizing the land behind Killarney out towards the park entry area, but I'd want to see the station outside the Killarney hamlet walls. The park needs more indoor, family experiences and the Sim Building is far more valuable as a home for that than as a coaster station.