Characters whose death could make the manga more deep.
Obviously with the current angle, although some wouldn't like it, I think the death of Chouji and Neji could make the manga much more deep.
Aside from the current angle, however, I'm just going to list some characters in my head whose death could make the series more interesting:
One of the Jounins...maybe Gai or Kakashi
Orochimaru: He just needs to die
Iruka
Tsunade (although not until a long while)
Jiraiya (maybe while he is in mid training with Naruto against Akatsuki members)
Also, when will Konohamaru and Naruto have their battle over Hokage that they said they would have since episode 2??