A bit of a strange idea possibly, but could it be interesting  having an option to carry over a number of (or even all remaining) troops and/or resources after winning a game into the next one? This could be e.g. a selectable option to use this as starting conditions for the next game.  For balancing, of course, all other parties in whatever SP or MP would need to be given equal resources/troops to start with (with an equal mix). With this, a campaign like e.g. "Alexander the great" co