i would stay away from stamped steel for a mask. that stuff may look and feel tough, but it doesnt handle impacts very well.
brass mesh isnt much better, it is far too soft. stainless steel heavy gauge woven mesh is by far the best material. you can heat to to make it malleable, then temper it to make it super hard and flexible.
there is a company here in Toronto that sells different kinds of wire mesh. im going to get some stainless steel mesh in different gauges to see which would be best for airsoft.