^^^
World War Z needs to be done in the style of Ken Burn's PBS documentary series The Civil War for it to really work. IMO (a mix of "archival footage", interviews, etc.). Although, not sure that would fly as a two-hour film as much as it would as a mini-series for HBO or some such.
I think it can work if it's done in a tone similar to District 9, but it can't stray away from the documentary format like D9 does.
Or they might decide to focus on fewer perspectives and go the flashback/narrated route with Pitt as a survivor of the war telling his story. That could work too, as an adaptation.
Pitt as the Narrator.