About a year and a half ago, I gave a shot at a WoW expansion idea, right before the Reveal of DF.
While I doubt that almost anything of it would ever be used by Blizzard themselves, at least narratively I wish they had the courage to do away with characters that have served their purpose and add new ones to continue the tale.
I also wish they would fix some of the degenerate gameplay designs from all types of content and class design.