Actually, it could be an option in the "Preferences" area. If you see the AI approaching with what you feel would make the difference, uncheck it and that single battle will take longer; check it again after that battle.
That would add minimal length to the game, while providing for the option.
You'd only really want to uncheck it if the AI were approaching with a superior force to yours for at least 1 unit, and you felt your bonuses for defending didn't complement their plusses, but you could win if there were some troop you could throw as cannon fodder to buy an extra turn delay. In general, the best defender is best, but not in that specialized circumstance.
Sam
That would add minimal length to the game, while providing for the option.
You'd only really want to uncheck it if the AI were approaching with a superior force to yours for at least 1 unit, and you felt your bonuses for defending didn't complement their plusses, but you could win if there were some troop you could throw as cannon fodder to buy an extra turn delay. In general, the best defender is best, but not in that specialized circumstance.
Sam