[Build-It-Break-it]

I think if weight savings was what your after I think making carbon fiber quarter panels and a roof skin would probably make more financial sense for a company. That would be in addition to installing a carbon hood, trunk, fenders, cowl, etc for weight savings. But then your crossing over into a full race car and less "street" car.

There's a company I believe that already makes a full carbon fiber body. But again not practical for a "pro touring" car. A carbon subframe will never happen unless someone is just doing it to show off and waste money. It's just not practical And in my opinion no real benefit.