I like the fact that we meet Denethor in his descent into madness...
Can't agree with this, Faramir was the heir to the Stewardship, and he would have made a better Steward than Denethor. I had hoped that Aragorn would keep him as Steward, since the title came into existence when the old kings ruled, after all, rather like the major domo (Mayor of the Palace) of the Frankish Merovingian Kings.
Perhaps it was felt that since they had virtually ruled Gondor, it would be uncomfortable to keep them in the capital. Of course this is all much more political than Tolkien ever was (just let us FR types arrange things in Aragorn's kingdom politically, right!)