Not knowing much about previous seasons of DW (prior to Nine), I think it would be interesting to give the Eleven a more mature companion (say Donna's age) to shake up the companion/Doctor bond a bit. I'd love to see a companion instinctively trying to parent the young man who's actually over 900 years old.
In recent years we've seen most of his companions have a crush on him and I think many in the audience may be expecting that. It would be interesting to case in a way that make shake up that expectation. It seems like many people don't expect romantic pairings to come from younger men and older women being cast together (remind me to mildly rant about that somewhere appropriate).
In truth, I would love to see Donna back. Since Matt seems to have a similar energy to DT in his interviews, but Donna did not have romantic inclinations for the doctor, I see a lot of potential story there.
Edited by TheLabRat, Jan 11, 2009 @ 8:41 PM.