Pretty much the same way you could do it with any other manufacturing/industrial process. Imagine re-creating a fairly large complex project without access to

Pretty much the same way you could do it with any other manufacturing/industrial process. Imagine re-creating a fairly large complex project without access to any source control, build systems, or bug reports. It'd be easier than starting from scratch, but not much - especially for hardware, all the tradeoffs and manufacturing tricks you had to investigate and implement your devices would have to be recreated. Your end result would probably look similar, but the way you get there would be different. Just like the wings on an insect are different from the wings of a bird.