Looks cool, good ideal
Sort of like a inkjet printer or plotter. I always thought it would be great to have a CNC magic marker or paint pen for marking metal.
The problem like large printers and plotters is they are made for printing on paper. If they could use paint (either solvent based or oven cured) on to metal parts it would be like a metal baked on enamel finish on metal parts.
This would be great for outdoor signs. Sort of like traffic or highway signs but with finer lines for pictures. The Dots per Inch on a aribrush is what 4 dots per inch?
The problem with printers and plotters is the limit on amount of different colors unless you mix colors. Getting the colors on a computer screen and what is sprayed or printed on metal to match I would think is not easy. The technology of inkjet printers has come a long way what with 1200 dpi or higher printers. Too bad the ink cartridges cost so much.
Maybe there are sign making CNC machine companies that sell a spray unit to go on a torch or plasma CNC cutting table that you could also use??