A simpler way to look at this would be to see Ive having been promoted to, effectively, the new Steve Jobs: the overseer and arbiter of taste for anything and everything the company touches. One difference: Jobs, famously, was intimately involved with Apples advertising campaigns. Cook, in his internal memo, wrote: Jonys design responsibilities have expanded from hardware and, more recently, software UI to the look and feel of Apple retail stores, our new campus in Cupertino, product packaging and many other parts of our company. But, still, its hard not to read Cooks description of Ives responsibilities as pretty much matching those of Steve Jobs while he was CEO.
Lastly, a title can just be a title, but Apple has only had three C-level executives in the modern era (excepting CFOs, whose positions are legally mandated): Jobs (CEO, duh) Cook (COO under Jobs, now CEO), and now Jony Ive (CDO).1 Its possible this title is more ceremonial than practical, but Tim Cook doesnt strike me as being big on ceremony. Apple doesnt exactly throw around senior vice-presidentships lightly, either, but a new C-level title is almost unprecedented.
I can see Cook-Ive as a sort of titular reversal of the Jobs-Cook C-level leadership duo. Cook oversees operations and running the company; Ive oversees everything else. So they created a new title to convey the authority Ive already clearly wielded, and promoted Dye and Howarth, his trusted lieutenants, to free him from administrative drudgery. I could be wrong, and well know after a few years, but thats my gut feeling today.