This does have some applicability to an idea I had regarding using the general in battle. You could use a two-step system:
1) A Marshal's ability to command an army in battle is related to his Leadership skill. Put too many nobles under his command, and he is less effective. The higher the skill, the more nobles he can command before getting a penalty. This could help keep army sizes down. Realms will want to have multiple, smaller armies.
2) In order for multiple armies to work together effectively, you need a good General, with appropriately high leadership skills. So if you have 4 or 5 armies trying to work together in the same battle, you would have to have your General there to coordinate them all. If the general isn't there, the armies suffer some sort of penalty. But if the's there, and he's good, then you get a bonus.
The idea here being that you need characters with actual experience leading your armies. This could help curb some of the situations where a new character played by an experienced player immediately gets appointed as Marshal/General because the realm knows the player is good.
It should be a combination of penalty/bonus. So as your leadership goes from low > medium > high, it goes from penalty > neutral > bonus.
As to what exactly the penalty/bonus should be, I'm not exactly sure. Morale doesn't seem to cut it. Maybe some modifier to effective CS. Trying to put 40 nobles under a Marshal with 10% Leadership should make the whole army less effective. Maybe a 10% penalty to CS? Dunno... just batting around ideas.