I'd really like to see the setting in Tevinter, because it gives us a chance to see a different culture of Thedas, from the usual ones. Maybe see how mages with no political power are treated or see slavery in the Imperium, since Dorian said how much of a culture shock it was, seeing no slaves in the South.
And, of course, showing how not every Magister is a card-carrying evil villain, but they are all different in degrees and have different goals; with people like Dorian and the Lucerni as their most moral, Venetori supporters like Erimond at its worse, and others in between.
Seeing an entirely different society and culture, with different views and customs, first hand are part of what made DAO so interesting for me.