Since he's basically running tractor tires..... Rayburn, or some place like that, we have them come out to the farm all the time.
I once ran a deer antler (nice 8 point hehe) through a tire on the tractor and we called in the location... they came out and replaced the tire and disposed of the old one. hands free for us.
And you can change them yourself if you have a spare rim and tire..... I have done this on combines (used a fork-lift) and tractors (used two 4ft bars to pry and align lug holes)
With the weight this vehicle should be at, and the heavy duty'ness of the tires, I don't anticipate he'd have many issues with flats.
But i believe he is making a custom trailor with space for spares.... I just had an idea, you could put a tire hydraulic arm like what they run on IH service trucks just for that occassion!!! but it prolly wouldn't see that much use... and are you gonna liquid fill the tires to keep the center of gravity lower?
Frank