GVWR is a theoretical number that is used for the DOT and state DMV. The GCWR is a real number in terms of what the vehicle can handle in total weight of the truck, passengers, gear, and towed load.
Less than 3% of the load over the rear axle of my truck is transferred to the front wheels so I do not worry about the frond and focus on the rear. The axle and wheel bearings with SRW are not the limiting factor, only the tires and springs, both of which can be upgraded.
Easiest and cheapest for the factory to add two more wheels but if I wanted more capacity I would do what is done with military vehicles and go higher rated tires like 19.5 ones.
Over 29,000 lbs. total weight for the vehicle and trailer and you pass into commercial trucking territory where a special license is needed and insurance costs more and there are other costs that should be expected.