Expecting to scrap an entire car because of damage to a portion of that area is ludicrously bad design. It isn't just major collisions that can do it - having to make an emergency swerve (such as for a sudden kid in the road), and hitting a curb could do it. On any normal car, such a repair would be a few hundred dollars in parts and labor.
That's a secondary issue, though. That area takes an enormous amount of the stresses on the body. Even if you assume that the current construction is connected together in a solid immovable block rather than having some flex room built into it (there are pros and cons to both) it will be taking enormous forces when the car is in motion. A small void or stress fracture? Your car might literally snap apart while you're accelerating onto the highway. Guess what issues become more likely the larger and more complex a casting or stamping gets.
People don't avoid doing things that way because it is technically impossible, or because they'd really like to do it but it is prohibitively expensive. It isn't done that way because trying to make that as one part is so mindblowingly stupid that anybody who doesn't happen to own the company would be fired for the mere suggestion.
When there is significant damage to the body, the insurance companies routinely declare a car as "totalled" and offer the owner blue book value in exchange for the title and car, and the car is either fixed and sold, or scrapped for parts. If the owner wants to keep the damaged car, they get less from the insurance company.
Just a couple months ago a neighbor got hit in the front right fender, hard enough to shove the right front wheel well a bit, but not hard enough to stop her from driving 25 miles to get home, and the insurance company paid her the max blue book of $11k in exchange for the car. This is routine.The wheel assemblies all put the stress into the main unibody frame, and neither the 72 pieces or the 1 replacement piece are involved in absorbing those stresses.
If your car snaps apart on the highway, it is precisely because you slammed curbs too often and bent some components of the wheel assembly enough to put it under additional friction or load stress, or someone took two damaged cars and cut and welded the unibodies together without regard for their role in load-bearing.
So, you really think that the engineers who designed and validated the new part design, and programmed the machines to stamp the piece, are so mindblowingly
stupid? They probably just cut 30 minutes off production times per vehicle and removed the need for 150 fasteners.
