If I recall and understand correctly, The Secrets of Castle O'Sullivan (the show itself) was long in development at the same time as some other concepts for Ireland, which ran along another project about ways to revive Hastings. However, SOCO was intended for Ireland, which was the park's plan B, should Hastings prove to be unsalvageable. Either way, the park was looking into building a new land, looking at about three possibilities, but ultimately, Ireland was the most appealing of all options to their clientele and seemed to management a perfect fit for Hastings, which needed an overhaul anyway.
The Dragon Drop Tower was a concept exclusively for Hastings, which by itself, probably would have cost about as much as the entire Ireland makeover (just guessing). Therefore, the park scrapped the idea. I doubt we will ever see that exact concept again, but apparently, the idea of a more generic shot and drop type of ride located in Castle O'Sullivan survived into the early stages of development for Ireland. The idea was shot down early on, in favor of a more conventional show that followed in the footsteps of one of Hasting's oldest and most beloved attractions, The Enchanted Laboratory.
The idea of a similar ride in a different location sounds new to me and seems like an excellent addition to an area that is otherwise very ride-deprived. I think this could be the solution to an age-old problem for the park: to keep Ireland from going the way of Hastings.