So I have an odd theory regarding AKB0048 and I'm not sure if it has been brought up before, but...the Center Nova's place on the stage is known as "position 0" and she's supposed to be isolated and alone, which is part of the reason why some of them disappear to save everyone. Nagisa and Chieri are both shown to have the potential to succeed Acchan and become a Center Nova. The show is called AKB0048, and the logo is two 0 rings overlapping each other. What if the ending involves two Center Novae, both inheriting half of Acchan, and they open the gate together to let everyone back? Lol.
Pretty much in line with what i was thinking of that, and it fits in with how Nagisa is and when she shines the brightest.