Sometime before DA I believe I outlined my own imagination of what could replace DD, and because the idea I came up with was based on the Dragon Challenge theming and coaster elements that people wanted to see in Gringotts, the design became an unintentional prequel/sequel to FJ.
Essentially, my idea was based on the hope they could cram as much as possible into the DD space, adding a second alley to Hogmeade looping right from the seating area and remerging at the end of the town as it opens to the stage and the path to Hogwarts. From there I saw fitting a forbidden forest ride and pushing into the far upper corner a new DC the size of Hulk. the queue buildings would be disguised as mountainous rockwork.
Essentially, the ride itself would use the drop-track mechanic with a show area based on the dragon arena from the forth film mixed with the stadium covering from the World Cup, (the rock-work could have a fake miniature exterior arena atop the mountain) The cars of the coaster are the stadium seats which rotate into position, but not before Dumbledore introduces the challenge and the dragon through a dark gateway in the arena wall. The handlers loose control, fire shoots out, and it breaks from it's chain. The Horntail disappears into the dark and flies out above via the silhouette projection effect through the arena-covering tent. It could even be torn by the Horntail. Dumbledore casts a spell which sends the track with the cars crashing down through the 'wooden stage,' each car spins to face left as the Horntail AA crashes through the arena before spinning right and launching to 'escape' into the ride. I imagined a second forbidden forest ride which would be a slow dark ride using the thestral carts or the flying car, with a forest queue which gets denser before transitioning into an artificial forest interior.
I may be asking for too much out of this.