Fan Casting Plot Outline Part 1 in Doctor Who: The Time War (2012)

OK so I'm using Night of the Doctor as a template for this movie idea. Cass still meets the Doctor at the beginning of the film where he offers to rescue her from her crashing ship that's being attacked by Daleks. Unlike in the minisode, she's more reluctant than angry to get on board the TARDIS. However, she decides to join the TARDIS, bitterly telling the Doctor that he has one chance to prove that he is "one of the nice ones". With that, the unlikely duo board the TARDIS (the console room being a recreation of the one from the TV Movie), and escape the Daleks. As the two fly through the Time Vortex, the TARDIS begins to shake violently. As the Doctor figures out what's going on, he learns that they're being pulled to Gallifrey much to his shock and Cass's horror. Upon arriving, the Doctor tells Cass to stay in the TARDIS as he investigates outside. Of course, Cass ignores him and follows the Doctor. Once outside the TARDIS, the Doctor is encountered by his old friend, Romana, who reveals she was the one who called the Doctor to Gallifrey. She informs the Doctor that a group of Daleks, known as the Cult of Skaro, have stolen a weapon from the Omega Arsenal. The Doctor initially refuses, not wanting to get drawn up in the war, however, he is convinced when Romana reveals to him how dangerous the weapon is, learning that Rassilon had his scientist, Roppen, make it capable of destroying whole galaxies. The Doctor is immediately convinced that no one should have that power, Daleks OR Time Lords, and asks Romana if she knows where the Cult is headed. Romana tells the Doctor that she suspects it's at a gathering of the remaining Temporal Powers, a alliance the Time Lords hold with other Time-Traveling Races, near Karn. As the Doctor departs, we see someone hidden in the shadows, listening in on the conversation. We don't see who it is, but we do see them grin evilly before they leave.