AKB0048/WMG

Tsubasa has an ulterior motive for being 0048's producer.

 * In the OP, there's a priestess-looking character who looks a lot like her.
 * One of the priestesses in episode 3 talks about needing to inform "Tsubasa-sama".

When the idols "graduate", they are fed to that giant entity that is being worshiped by the priestesses.
Mostly because we never get any indication of what happens to an idol after they "graduate", or what happened to previous generations of idols.
 * Possibly Jossed with the discovery that Idols are the only able to attract Kirara which provides the galaxy with clean efficient space travel. Compared to the Dualium which require a lot of effort to mine and refine.

Chieri's dad's corporation is a supplier for DES.
"Chieri: I knew it. This machine..."

Chieri suceeds Takamina and Nagisa suceeds Acchan.

 * Which is suggested by their arrangement in the lineup.