I'd say that what you posted is well worth 2 cents, and then some. So often we want absolute answers to things when there are no absolute answers to be had.
I don't believe in magic numbers. There is no threshold where on one side everything is good/safe and on the other side everything is bad/dangerous. There is no black and white in life. Reality is entirely gray. Since a manufacturer has to come up with something and they can't say, "People with good sense do this and people without good sense do that." they have to come up with a one size fits all.
If you put a camper on your truck and then go slalom racing you should expect to have racing stripes down the side of the truck and camper shortly. There are idiots who would find themselves looking at the world sideways and blame someone else for it though so GM has to come up with something. GVWR, AWR, Camper WR and towing ratings are guidelines more like the pirates code than the speed of light.
That being said, as you exceed these ratings you accept that the results are less predictable and you must accept responsibility for the consequences. For example, winch ads often show a truck with a monster camper on its back being pulled up the side of a mountain by the advertiser's product. Almost certainly that truck illustrated is overloaded in several ways but the important thing is that it is being used in a way the manufacturer would never condone. If you want to take your mobile apartment to the top of a mountain to hunt sheep, go ahead but know that you are way beyond any sanctioned use of the truck.
The more stress you put on a part the shorter its life will be. I can't think of any exceptions. If you start with a K2500 and put a camper shell on it with some sleeping bags and a bit of camping gear in the back then it will possibly go a million miles. Replace the shell with a 12 foot dry bath camper with 3 slides and 250,000 miles might be all there is. If you take that rig to the arctic circle to see what all this noise is about global warming and decide to do a bit of rallying along the way then you might not make 100,000 miles. If you love rallying big campers then that is the price you pay for the fun you have.
The right person could put a great whopping camper on a half ton truck and tour the country with minimal fuss but few of us are that person. It is best to pay at least some respect to the manufacturers ratings. Most people get over those limits when towing or loading the bed. One time I filled the back of a Nissan pickup with so much railroad rail that it was sitting on the bump stops. I drove it home that way, about 30 miles. I took it nice and slow and tried to miss as many irregularities in the pavement as possible. As far as I could tell there was no lasting effect of this gross abuse but if some problem had cropped up I would have only blamed myself.
Springs are the first thing to show the strain of overloading. Consequently they are the first thing to get upgraded. It is often overlooked in these cases that shocks have to match the springs. If something is done to increase the spring capacity then the shocks need to be replace too. Equally important is sway control. Just because it will hold the weight doesn't mean that the truck will stay upright. Sway bars are an important consideration. The funny thing is that sway bars are dead simple. I've made several in the past and they work just as well as store bought bars while costing much less.
Once the suspension will hold the truck up the tires are next. Some would put them first. Again there is nothing magical about tire ratings. Typically load ratings have a temperature component. The faster you drive the more the tires heat up. The hotter they get the less load they can carry. No manufacturer is going to tell you that you can safely run their tires at 50% more than the sidewall rating just because you never go 130 MPH while carrying your camper but the truth is you probably can. You just can't do that and never check the tire pressure or temperature too. Keep the pressures up and the speed/temperature down and the tire will easily handle more than the sidewall says. Wheels have weight limits too. I'd be more concerned about overloading the wheels than the tires.
The axle is next. You could put a heavier axle under your truck but at that point you might be better off replacing the whole truck. Typical axle maintenance is to check for leaks at each oil change and check the gear oil level if any leaks are found. That's it. No changes, flushes, inspections or other maintenance is usually done. And for "normal" service that may work but for the sever service of towing and hauling it isn't enough. You need the best fluid you can come up with and it needs to be kept fresh. If you drive through a river to get to that idyllic camping spot in the woods then the price is a gear oil change asap. At the first sign of distress a complete inspection is in order. Every time you do brakes you need to inspect the wheel bearings with an eye toward replacement if there is the slightest hint of distress. The harder you push the equipment the more you need to baby it.
Frame failures are rare but they do happen. If you are well beyond the recommend limits then you need to consider maintenance that others don't even think about. Every time you get into a situation where the frame is tweaked hard or the road is rough you will need to have a look at the frame. Cracks nearly always originate from weld points or holes drilled in the frame. Give them all a good look. Suspension attachments are a prime location for frame problems. Frames can be repaired.
Something almost always overlooked is the bed. Go look at how your bed attaches to your truck. There isn't much there. If you attach a big camper to the bed it will put a lot of stress on the bed mounts. If you are going to push the limits it is better to pass the stress directly to the frame than to take it through the bed.
Ultimately truck weight ratings are about legal liability. If your warranty is gone and you can accept responsibility for your life then it's your truck. Do what you want to do. I'm sure the cops will understand too.