Why doing a shitty job should be treated as a crime? You promise to install twenty five year shingles but you use a much cheaper brand and the roof leaks in three years. That's not a shitty job. That's fraud.
Sorry Argus. I'm going to pick apart one of your models, which of course is irrelevant to your point!
I have some roofer friends. There's more to the problem with shingles you describe. For the past decade, roofers have been installing 25 year shingles in good faith, only to have them fail prematurely. At that point, the manufacturer starts dodging and the installer gets caught in the middle.
You see, we had shingles for decades and decades that would last 25 years. A bit less than 25 years ago, the eco-warriors began to attack shingle manufacturers for some of the ingredients used in their making. There was a lot of petrochemical thingies and some <gasp!> chemicals!
So some of those ingredients got banned! As is the norm in these situations, the eco-warriors and the politicians who backed them took it for granted that there were substitutes. Perhaps there are, but the shingle manufacturers had to provide shingles IMMEDIATELY!
The biggest problem is that there was no time to do lifetime real world durability tests. They had to do accelerated simulated testing in their labs. These are always a poor correlation to actually letting products age for the actual number of years.
Guess what? A lot of shingles didn't last as long as they thought! So we have a lot of upset customers. They go for the installer first because he is the most visible but the installer has no control over the product - he didn' make it! He has to take the manufacturer's word. The manufacturer of course has more expensive lawyers!
Once the whole process was so reliable that the few times they had failures the shingle company would cover the entire cost of replacement. Those days are long gone. Modern warranties are ONLY on the actual cost of the shingles and are pro-rated against how many years they were on the roof. With most failures, the actual refund to the roof-owner is only a small portion of the total cost.
Most fraud with roofers is much simpler than what you describe. The scoundrels simply ask for half the money up front and then disappear!