I know what you were saying, it it's a novel idea in it's own right. It's just a tedious process to fix a body after a hit when it's metal. It's definitely a "cool factor" for someone that can do it.
I just look at it from a manufacturers point of view also. A die would have to be made to stamp it out of sheet aluminum and it's not gauranteed that a universal fit will allow the everyday modeler to be able to fit the shell to the car.
Fridge, the best way I can see for one to be made from scratch it to form a body shape out of wood and bang as well as weld peices into shape. Annealing the aluminum to make it more pliable and accepting of shapes would also be necessary for complex shapes. English wheel is also good for getting curves in the metal.
If you can get a teacher to coach you through this process, that would be great. metal shapping is an art that is becomming harder to find these days.