I know some of you quys have thought this over before. I have unintentionally breathed in oil and diesel mists and naturally avoided any connection to a oiled compressor. The e-tailers bold enough to give the price on the Bullard hood list @ $600+ for a hood and cape with 5 or so ft. of hose and a belt. "Request for a qoute" sounds like heavy middleman action on other sites. That is a little over in cost. Maybe they have a regulator or other components that might work in a DIY system though.
The scuba face shield could be protected further with a cheapo HF face shield, but yeah, eventually time would take it's toll. Maybe some drops of contact cement strategically placed and a sheet of plastic put over the lens or a combo of the two. Surely the other components would last as long as safety gear parts, but I've never used scuba gear myself to know of the build quality. Still seems to be feasible in my mind.