CCS Trans grad here working Alias at the big three. I think it'd be a cool design project, but not an easy business plan. As others said, you'll really have to sell it on the aesthetics side, then say, "by the way it'll increase your MPG by 10%". Almost no one's going to spend hundreds of dollars for unpainted high-MPG body panels.
Look at this-
GPRauto 92-95 Civic Closed front end
Without the lip, it would be an awesome ecomodding bumper. It's even good for racing, on a popular platform for both. But for $350, they have only sold six of them (I'd buy one at $50). You need volume to get the cost down, but you need sales to get volume.
My advice would be to build an aero kit for your own car, style it really well (and tastefully), and calculate the fuel savings. If someone wants another, use your leftover plug and make one.
A fun paint scheme helps. You should have seen me rolling around the CCS campus in this...
