Uh. I appreciate the effort, but contemporary Total War titles are boring to play, I don't know how boring they could be to watch.
That said, I'd love to see The Last Roman DLC if you have it (and its smaller scope would ensure more chances of it ending). If not that, the reply is obvious:
Western Roman Empire, Hard.
Lemme remember happier times.
(I'd guess that, if you want to play a mind-numbingly difficult Total War campaign, the Medieval II Warhams mod would find more love from the Playground's denizens. Plus it's Russian hard, and we can all cry for the end of the Old World and spit at the new Total War: Warhams).