One way to mitigate the pinch of supply-line issues is to be nimble when implementing substitutions.
In some cases material substitutions like a range of material thicknesses are already specified in the "Notes" section of the part drawings.
In other cases, particularly with cast materials, there are often "sister" alloys with slightly off-set (but overlapping) alloy composition or microstructure. It should come as no surprise that alloys with wider ranges of alloying elements allowed are less expensive and more available than alloys with very tight tolerances. The wider toleranced alloy allows for a greater percentage of scrap and post-manufactured re-melt while tighter toleranced alloys require a greater percentage of virgin materials.
One of the more vexing impediments to making substitutions involves the documentation required to verify compliance with a host of Federal regulations.
For instance, Fuel Economy is determined, in part, by what weight class a vehicle is in. That weight-class determines the drag used in the dyno rolls and they are broken into classes of 125 pounds each. It does not take very many substitutions to jump to the next weight class and potentially invalidate your fuel economy certifications.
In a similar way, something as simple as substituting a brand or size of tire that is more available or filling engines with 5-W30 oil instead of 0-W20 oil will materially impact the fuel economy of the vehicle as-delivered.
Other major categories of regulation include how the vehicles protect occupants in crashes and tail-pipe emissions.
It is my slightly informed opinion that modern automobiles have many layers of redundancy. For the most part, they meet tail-pipe emissions standards even when one or two sensors fail. The problem is that the vehicle is materially different than the one the factory certificated as meeting the Federal standards.
From a crash standpoint, there is a great deal of latitude between airbag Deploy and Non-deploy events and minor substitutions in alloy or thickness might move the Deploy/Non-deploy threshold. For example, the airbag might deploy when hitting a 150 deer at 50 mph vs. 45 mph for the stock vehicle.
The real-world issue is that as new vehicle production is choked-off, the fleet ages and the less affluent end of the market is stuck with vehicles that should be scrapped. Or less affluent people make-do by cramming more people into the few vehicles that are still running.
The change in crash performance in new vehicles is microscopic compared to the degradation seen in a thirty year-old vehicle from areas where dirt roads are hit with chloride, salt is applied to snow or where salt mist from oceans is carried inland. The effect corrosion has on the structure that absorbs the energy of frontal collisions is relatively small because the metal is thick but the same cannot be said for the thinner metal that absorbs energy from side and rear impacts.
Regulators have the power to soften the impact of supply-chain shocks. They also have the power to make the shocks worse. The question I want them to ask is "Do I serve the American public or do I serve the regulations?"