Regardless of how well you build the machine you will need an extraction and filtration system for plasma cutting. The fumes from plasma cutting are very bad for you even from mild steel and get alot worse if you attempt stainless steel. If you are going to cut different thicknesses of material you really need to be able to set an initial piercing height and then a cutting height once the arc has been established. This is normally done by setting the piercing height with a foot sensor or can be done with a touch and retract sensor then switching to arc voltage height control to keep a stable arc height. This will add considerable cost to your machine. Also with plasma cutting thicker material the machine requires a delay to allow the plasma arc time to establish and fully pierce through the material before the drives turn on and move the machine.