I'm pretty sure that if I sat down and thought about this and did the math behind it, I could make it.
I would just require a man to dig the trenches for the posts. Then again, I could have it slightly elevated off the ground, and just make the hill higher to compensate for it. At the same time, I think that could potentially impair its stability so... Yeah. My future hubby would dig the trenches, I would do the math, and at the end of it all our kid(s) would have a roller coaster.
Then there would be oil involved, a control panel either attached or not. Not that hard to make a remote connecting one thing to another really. The only problem might be the creation of a vehicle and various safety devices.
Read the title, thought "Love me?"
Saw the youtube thing, "Oh, that would have been nice too."
"THIS GUY WAS ABLE TO BUILD IT IN HIS BACK YARD! WITH A BOX OF WOOD, PVC TUBING AND SCREWS!"
Actually, I am confused by what you mean of "belt devices with hooks." I'm going to guess....a lifting mechanism, so you don't need someone else to lift the car to the top?
PFFFT, if you're bringing motors, and lifting devices into this, lets go all the way with a magnetic launching mechanism that hurls the kids at the hill at 40mph!