Plasma Torch

I am considering building a CNC plasma cutter, and while
looking around I see refrences to drag shields, which allow
you to place the tip of the shield directly onto the workpiece
when you cut. These will keep the tip at the proper distance
from the work. Could these be used in a CNC setup? The Z
axis could be spring loaded down, similar to a floating engraving
spindle. Any idea if this would work, anyone done that, or do
I need a torch height control system like rutex sells?

http://www.rutex.com/953004.pdf

Thanks,
Bill