I think the fundamental issue I have with the other Total War games is, as well as the tactical interface works for other historical periods, it is difficult to find an equally dynamic, involving setting for a grand campaign.

At this point, I'd be delighted if the next Total War game was simply an updated Shogun with more choices for the use of ninjas, better graphics, improved terrain that better reflects the battlegrounds of the Sengoku Jidai, etc.