As already hinted to in the thread, insurance for this is stupid high, signed waver or not. My dad's shop has 2 lifts, and his policy does not even allow anyone other than him or his few employees to stand under the lift. The insurance policies that would allow non-employees to work under the lift were just plain ignorant.
Anyways, if you find a way around the BS insurance, I wish you luck with your idea. I know a lot of people would pay that much to prevent crawling on their hindside all day.