Perhaps the largest mileage gains in recent history occurred with the radial tire. And then the trend went towards wide and low profile with no way to shield the front of the tire from the wind, we lost part of our gains. And raising a truck exposes more of the upper half of the tire. Which is going 110 MPH wind speed. I was amazed to find out that Indy cars are limited in speed primarily because the top of the tire is going 460 Mph wind speed. And that's a slick.
The front surface of a truck could be raised or lowered based on the ground clearance requirements. A trucks cargo and passenger areas could change shape based on those requirements. I am talking conceptual here because as soon as I think in the box then, I am stuck in the same old mud puddle.