Not peasants... burghers are commoners too, as are the administrators of lower level land holders.
I've long been arguing that one should not actually be given such a large selection of flank commanders at all. What the hell is nobility good for when any duke or king can have his lowborn sergeant lead an army of 15,000 :wacko: Your baron, count and duke and vassals SHOULD rebel and torch your castle in protest, if you asked them to follow such such jumped-up two-bit jackanapes into battle.
I'm all in favor of restricting army and flank command to, say, the five or eight highest ranked nobles ACTUALLY PRESENT in that flank. As is, you can basically appoint anyone to any army leader position, regardless of where he actually is (i.e. when you select a commander for an army in Scotland you may even appoint a guy who is already commanding a regiment in Anatolia....) Army leader appointment is sooooooooo horribly wrong!!!!