I personally disagree with this. What makes one army different from another?
Equipment, loyalty, health, and experience. The first three are fairly written
right now. I like Scott's idea of a more simplistic quality rating for all the
"hired factors", whether they be troops, shipbuilders, etc... This allows for
some minor development of the men you control. If you use the "no skill
rating" system, there is no chance of development for them, other than giving
them better weapons and making them fanatical to you.
If someone can afford to maintain an army for a long time (and this indeed
should be difficult), have a lot of battles with them, and possibly get someone
to teach them the finer points of pigsticking, even farmers would learn to
point the business end of a pike at the enemy.
There should also be the possibility of trying to recruit those who do this
type of stuff for a living, whether hanging out in a city for The Commando
Men(tm), or trying to recruit inside a shipbuilder's tower. If you've got the
money, are "famous" enough, and are in the right place, you should be able to
recruit people that are fairly adept at what they do. These types, of course,
would be fairly rare to come across, and can only work for one player character
at a time.