I have been dreaming about this same idea for some time, since I don't like either so much the smell of exhaust fumes. And as my old summer vehicle is not so leak tight, some of the smell comes inside the car.
Anyhow I think that the ignition system should also be in good condition to avoid unburnt fuel entering the cat. The fuel in the cat would cause excess heat that can melt the cat.
To minimize this risk of melting I would put the cat more far behind from the engine.
I'm not so sure if the A/F mixture has to be exactly right because also the newer cars run rich when cold and that does not kill the cat immediately. It just doesn't clean all the pollutants 100% Or what do you think?
Well these are just my thoughts, I cannot be sure since I haven't tested it.
Maybe next summer
