Following some creative differences with Warner brothers Ruari decided to depart the project, leaving us to speculate what caused the departure. After looking through the work that Ruari oversaw for the Akira adaptation though, it seemed like he was planning a surprisingly loyal take on Otomo's groundbreaking manga/feature. Concept art seemed to indicate that Chris Evans would take on the role of Kaneda with Joseph Gordon Levitt playing the tortured Tetsuo. That aside the designs stuck pretty close to the originals including Kaneda's iconic light bike, which I'd like to think would be hailed as 'f***ing genius' by ad placement executives on the project.
While we're left to speculate what could have caused the project to die on the vine I'm guessing it probably had to do with deviating too far away from the source material, which seems to be a common predicament with adapted films. Do people really want to see a live action adaptation of Akira? While the initial reaction would probably be a hell yes, the reality is that a botched adaptation would be most likely in the hands of Hollywood 'idea men,' who seem to always see it fit to deviate from something that was never broken to begin with. If you're craving your Akira live action movie just watch Chronicle instead, an underrated gem featuring the same archetypes present in Otomo's classic.