If you've seen the Shogun 2 cinematic, (let's face it, who hasn't) you'll see two men dueling before the battle. What if this happened in every battle. Two soldiers duel to gain some perk for the future battle, i.e extra accuracy for archers or improved charge/melee attack for melee units. AND just like battles you could control a soldier or auto resolve. That would bring a boost of excitement before a battle, getting you pumped for the battle ahead!
I know my idea won't appeal to all but for those who like M&B this would have been very enjoyable... If done right!