Patent law requires something to be "non-obvious". It cannot be a single step away from a previous patent. This patent would count as prior art for such an obvi

Patent law requires something to be "non-obvious". It cannot be a single step away from a previous patent. This patent would count as prior art for such an obvious change, and as such the patent you describe would not be valid or granted. Non-obvious is supposed to be a broad term, but in reality a patent examiner will just search through prior patents for prior art. In this case, if you really did copy everything else word for word, he or she would very quickly find the existing patent and deny you.