[darksofa]

Only the most critical layers use the most advanced litho tools. The other layers use n-1 and n-2 litho tools and print larger geometries. You are correct that it is not a problem to print larger geometries.

However, there is more to it than just litho. Many thin films, implants, etching, polishing. A product is designed to a specific fabrication process flow. The real showstopper is that the process flow guarantees the electrical parameters of the transistors and passive devices will be with a certain range -- the product circuits are designed based on these parameters' values. A different process flow has all different electrical characteristics and the product won't work without redesign.