I've been thinking about this for a while and want to basically combine two coasters in one. I think my perfect coaster would be a wooden hyper (or perhaps a hybrid, with steel to create the large hills and then a completely wooden structure for the lower terrain parts).
It would start off stupidly high with sustained ejector over about 4 large hills - B&M style. Ideally the first part would start over a gorge so that the sense of height and space would be intensified and so that there would be some stunning natural scenery. The second half would then dive down into the valley and be all sharp turns and terrain. It would have the speed and twistyness of a gravity group but with lots of lovely bunny hops and floaty airtime thrown in. It would be low to the ground and go in and out of the forest like Boulder Dash and have that classic woody movement to it. Perhaps somewhere in between the 'hyper section' and the woodie section I would maybe squeeze in Twisted Colossus' zero g roll.
Money is already no object here so what the hell, why not make it a racer too. The first half wouldn't really matter but once in the valley, the two trains could travel the opposite way down the mountain crossing over each other many times.
Obviously, it would be themed to dragons.