Perhaps a better idea would be to have a standard bearer that all troops spawn from, who basically in his own unit. If he goes down, then another picks it up until that unit runs out of soldiers. Should no one grab it, reinforcements spawn from original spawn point. Oh, and obviously the player himself could carry it.
And yes, bring back the war chest. Too many times I've made inventory mistakes. But add that you can grab horses out of there too. Actually, now that I'm thinking as I type, instead of a war chest, add a baggage train. Maybe just a big, slow moving wagon (destructible) with arrow barrels and a spawn point. Push it too far forward and it could be captured, hold it too far back and its not as effective.
Traditionally, once the baggage train was captured, it was game over for the army, so no more spawns. Of course, currently the battles are too fast to do this. We'd need a little set up time (and so would the AI).
We do need Standard bearers. They were so important in medieval times that carrying one was an honour given to the most deserving, even tho it meant one of the best fighters was rendered incapable. For Fun's sake, give each unit a banner. If the Standard bearer goes down, the standard is picked up immediately by whoever is nearest. If the enemy pushes enough that the standard cannot be picked up for more than, say ten seconds, the unit falls back until a new standard bearer is spawned and they all follow him.
It would be annoying as fork, but definitely add something to the game.