That's a good point! And now that I think about it, maybe the Jing's pyraminx actually is a shape mod of the skewb? Jing's pyraminx has four centers and four corners which are akin to the eight corners of the skewb?A skewb is a deep-cut puzzle, and a pyraminx is not, but they are both 4-axis puzzles.
So yeah, we have enough shape mods of pyraminx, skewb, and NxN. We need more megaminx and square-1 shape mods!