What effect does tire width have? Very narrow (<165mm) tires vs dual tires of trucks for example. Smaller area of friction versus lower pressure
probably quite an effect, but reducing damage via width will also decrease vehicle efficiency and increase rolling resistance, so the gains at the road may be lost in an overall loss of efficiency at the vehicle, not to mention manufacturing and materials cost, when finagling the tire-width variable.
I don't have any numbers, though.
Not necessarily; one could formulate the tread rubber for such wider tires so they're less grippy per square cm of tread contact-surface, and so exactly as grippy as before per fully-loaded tire. Basically making every change in the opposite direction from what dragster tires do (other than the width.)