BruceW

You could be the next human subject Glados awakens, but Wheatley is finally able to get back with the portal gun on the moon (could be a hilarious scene between him and the "SPAAAAACE" robot) and He just wants to say sorry to Chell, Glados informs him, and He would ask your player to help,  The whole game could be a choice to either side with Glados (who is most likely giving you examples of how he failed) or Wheatley. During the entirety of the story could reference somehow Chell's past to sate the fans, and go from there.

This isn't likely considering Caroline's personality was uploaded to Glados, I.e. Cave stating "If he couldn't upload himself to a computer, Caroline would" And Chell is most likely related to some other Apature Scientist seeing as she entered her potato in the bring your daughter to work day thing, LOOOONG after Cave was Dead( Reference: Soon after the competition Glados kills all the employees at Apature. 

 This isn't likely considering Caroline's personality was uploaded to Glados, I.e. Cave stating "If he couldn't upload himself to a computer, Caroline would" And Chell is most likely related to some other Apature Scientist seeing as she entered her potato in the bring your daughter to work day thing, LOOOONG after Cave was Dead( Reference: Soon after the competition Glados kills all the employees at Apature
 

 That probably isn't likely, It is more probable that Chell is the daughter of another Apature Scientist considering she entered her potato into the Bring your daughter to work day thing, and  Cave was LOOOONG dead before that. And Caroline's personality were implanted into Glados, i.e. Cave stating "If he couldn't be put into a computer, Caroline would."