I had an idea back when i was about 16 of an inverted spinner, picture the seat's of insanity at stratosphere (best thing that relates to the original idea) on a 4 person spinner car but inverted with some creative track layout. free swinging inverted spinning action over a creative terrian.
This was an idea along with an inverted loop/drop as the defunct drachen fire, slightly steeper and of course a bit larger.... hmm maybe zero gravity roll to 150+ drop.... not sure if this has been mentioned.