Lenses could be made a lot cheaper by leaving out the shutter blades, and all that extra hardware. The lens could also be made much lighter. The complicated mechanisms could be left out, and just use faster shutter speeds. This could make those ultra-fast lenses available to the rest of us. Also, good idea about the welding goggles, as I have a pair somewhere that I may be able to adapt to the purpose.
I have a lens that is just an achromat meniscus, f 4.5, two elements and a diaphragm, about as simple as it gets, but it weighs something like 6lbs (did I mention it's a 16" Kodak Portrait lens?). So (relatively) small maximum apertures and mechanical simplicity do not a light-weight lens make