You do know that widening your tyres and/or track directly affects the turning of your vehicle and increases the loads on your suspension?
Purchase a new car and do a non-factory ''upgrade'', then take it back for a service. See how they react. A mate of mine had to remove his 70k worth of shocks, mags and tyres (not cheap, no name stuff either) from his Beemer as it was still under warranty. They argued that the vehicle was not designed to run with the sizes he installed and thus his warranty would be voided if something related to them failed, ie a suspension component.
Mods done by the local hot shop do not equate to factory-fitted options, which have likely passed necessary tests and will not affect the safety and handling of the vehicle.
Thing is, I doubt Audi Sport purchases a set of Bilstein shocks off the shelf. Those are more than likely designed and manufactured to the specs of their LMPs cars and that is all carried out by qualified engineers. Obviously Bilstein don't make nonsense off the shelf products, but, a quality, reputable product does not mean quality workmanship nor does it guarantee that the correct components in relation to the vehicle were used.
My argument is this; Audi Sport employs qualified people to carry out engineering work and has things specially made for their racing cars. There is no guarantee that a mod shop is run by qualified guys. They could be guys that have ''taught themselves'' and they are using universal products for a wide range of vehicles with differing baseline performance capabilities.
And let us not kid ourselves, the majority of mods are to do with looks and speed, not safety.