It seems many believe something happened to all Time Lords everywhere when it happened on Gallifrey. I've never understood that interpretation. I believe it only happened on Gallifrey, and anyone who wasn't on Gallifrey, wasn't Time Locked, Erased, whatever. So, If Romana was still in E-Space, she would be unaffected (Other than what happened to her Home Planet). If the Doctor went to the time and place where he dumped Susan off, she'd still be there (If she didn't run home to Gallifrey to participate in the Time War). This is why I think a Retooled Rani could be a very good possibility to be used as a villain in NuWho, because I think she would've stayed far away from Gallifrey and the Time War, unlike The Master, who could easily be lured back with the promise of more Regenerations, since he goes through lives like underwear and socks.
I do hope at some point thy bring Gallifrey and The Time Lords back. I don't wanna see them every week, or even every Series, but, I always enjoyed the few times they appeared in the Classic Series messing about with the Doctor's life and manipulatng him. I enjoy the Time Lord back stabbing Politics (The Gallifrey Adventures Audios with Romana II and Leela are awesome fo this, S5 coming out in February, I believe)
Regading Oswin The Dalek as a Companion - I too was thinking throughout Asylum of the Daleks how cool it would be to have Dalek Oswin as a Companion (Shades of Shalka Doctor with his Android The Master as a Companion)