There are tractors with loaders that can move pallets. One came up at an auction I missed last fall- the darned thing only brought $1400. Wished I bought it. But, I don't have one right now. It's on my wish list....

As for the tall sides, one thing you can think about for fuel savings and lower wind resistance is to make the sides have a rod halfway up that acts as a hinge. We had an old Omaha Standard hog rack back in the day that was like this- pull some pins at the corners, and the sides fold down over the outside, making it half-height (About as tall as the cab of the pickup). When you needed to haul an animal, you'd flip the sides up, put the lynch pins through to hold the sides up, and away you went. I hauled tons of computers with that rack back in the day with our old 1992 Dakota. The rack has been broken and fixed so many times that it's not really usable anymore, but it really worked slick back in the day