Yeah all of them are questionable. The only one that has even a tiny chance of succeeding is the piston idea. You don't have to pay for the weight and you only have to cut the circumference of the piston out.
The piston idea has a problem. Rock isn't like that. Natural rock does not often come as one big solid piece. It's more like a pile of boulders of different sizes. There are cracks, underground water, rubble, etc.
