A Holiday In The Park event would be a great idea. For the first time ever I went to Busch Gardens Christmas Town last weekend. It was really cool to be able to ride a roller coaster in December.
If Great Adventure did this, they would only have to open half of the park. They would close it off at the carousel and open the rides and sections on the right side of the fountain. This would also allow some coasters to be open. Dark Knight, Skull Mountain, Road Runner, and Blackbeard would be open most of the time. Batman and Nitro can be open weather permitting. Zierer rides can operate as low as 32 degrees and B&M rides can operate until it hits 40 degrees. I do not know the temperature for the indoor rides. All the other rides in those sections can easily be able to run. They could find room somewhere to put a light show and use Showcase and maybe the stunt arena for live shows. As popular as Great Adventre is, I can really see this working.
Hershey always makes me mad that they cant open Looper and Great Bear at Christmas. I been there at durring Christmas and it's been warmer than it was at Halloween.