Ben
No one including myself is trying to circumvent manufactures warranty wieght ratings. I'm calling them what they are. Legal ratings are another issue in the works since horse carriages from the early 1800s. Based on....yep, max lbs per inch width of steel rim on a horse carriage. Well before manufacturing orgs as we know them today existed.
When you go from a DOT class say 3 truck, which has a gvwr to fit an emissions rating, same everything else falls in the dot class 4, gvwr is based literally on the sum of the axles. For an additional 2000 lbs..
Many of us will question the manufacturer meanings. Or as soon pointed out, he licensed his midget Toyota at 10k lbs. I'd do that with my 1500 vs his other option of 7000. I can't buy a 7200 plate, choice is even 2000 lb increment. I'm good to 8000. Altho used car dealer was trying to sell get me a 6000. I'm like, uugh no! Legally I need to buy an 8k license. If I bought a 6k, I could only put 600 or so lbs in my truck.min plate is 1.5 time tare to next higher ton. 5400 x 1.5 is actually, 8000. That's what I'm legal too. Sum of axles is 7900.
Even with your ski lift designing. I'd bet at slower speeds you could move more wieght than higher speeds. You have to protect the riders. Road wieght laws protect the road beds, not the idiot at the wheel!
Trust me, an Leo will and can get an unsafe rig off the road, even if under whatever rating you want to use! It WILL hurt your pocket book! It EILL make your insurance go up, and not get renewed!
Being over a manufactures rating may not hit you. If said manufactures rating is OVER an FBL rating, that will net you a hole in your pocket book. Ie run down the road at 20001-25000 lbs on a 25k rated axle. You're over designed road bed limits.
One can't always use design numbers as safe, legal etc.
Unfortunately, with 40 yrs using dot class 1-6 trucks in business, I have figured out what is legal, vs warranty, vs smart too.
OP needs a truck that has 4500 or so payload lbs. Does not matter on badging. How that payload needs to be distributed on the truck, will also matter. I would want a minimum 4000 on RA available. After that, drive train that allows 30% min gradability in 1st gear, enough HP to pull 5-6% freeway grades in the 45-55 range. 45 is max min posted speed I've seen on interstate type roads. Wa st it's 40.
Choose ones poison, more than on way to skin a cat, or clear as mud for OPs question.
Marty