If you want to use wood ramps, then use them. Just buy 2x12's and start with say a three foot piece and cut the next two inches shorter and so on. Just stack up as many as you want. Cut them at an angle if you want, but not really necessary, in my experience. Screwed together the chances of splitting are mostly non-existent.
If you worry about them sliding on each other screw them together every time you stack another one. They are probably not going to be cheaper thought. A 12 foot board is going to get you about 8" lift. If you want to get really strong cut and fit a 3/4'' of plywood between each 2x12. Screw them together. Going to be heavy.
I don't think I would get much higher that 14-16'' with the 12'' wide boards.
They will not collapse. I've used them for a 36,000 lb. motorhome. People use 2 bys to level trailers and motor homes all the time. At least as secure as jack stands I would think, although not redundant.