I would really like to see a conquest mode, kind of like dark crusade or soul storm campaigns, but more in depth kind of like how total war Warhammer did it.
where you pick you leader/hero build up your army, build buildings like a barracks and armory, massive fortresses that would have to be sieged to take it over or destroy it. forge alliances with different fractions and destroy enemy fortress, and armies, conquer territories. You would move around the map territories with your elite units (other units would be grouped up with your leader and elites) in a turn based style game with a grid map (maybe have a random map generator so every game is different). Once you get into battle with a enemy it would load into the rts style game ( a.k.a Dawn of war) on a map with who ever you attacked or who attacked you. Through in some dialogue, and a quest system.
This mode would add a lot of replayability, it should be separated from the story campaign and skirmishes games, if you don't like to play conquest mode you wouldn't be forced to it would just be a extra mode like last stand was in DoW 2. Maybe even add a leveling, gear system for your elites and leader, skill trees would also be pretty sweet for your leaders and elites.
So it would me kind of a mix between Dawn of war, Warhammer total war, and a little bit of civilization