They don't get dull THAT fast.
Yes, the method you describe will work just fine.
Does your CAM system know?? Depends on your CAM system
The lower end .dxf converters pretty much do what you tell them to do, they just follow the drawing you give them. Most if not all 3D CAM systems do need to know the stock size. But you should always verify the code they produce "just in case"
I'm not sure if you'll be able to do exactly what you want in a CAM package. It shouldn't be too hard with a .dxf converter, though.