For a table purely designed for plasma cutting I don’t think that a motorized z axis is all that important. At least in a 2×2 form factor. It might be desirable to divide larger cuts into multiple cuts or just pressing pause to let the material cool down if it starts warping. The torchmate 2×2 that I use has a manually adjusted z axis and the above is all we do. Initially I was adjusting the z when the material was warping, but I have found that I just press the hold button during longer cuts or repeated cuts in the same area to keep the material from getting hot enough to warp in the first place. Doing so does cause extra points that are wider from initiating the arc if you don’t catch it between cuts.