[licker]

Ok, lets pick 'army composition' as the element to externalize. Lets ignore commanders and summons for now, focus just on balances with recruitable units.

First lets assume that the AI has a composite picture of its current nation every turn, that would be tresury, income, upkeep, resources (gotta break this one up a bit to capital, forts, and other) and existing army composition.

Now the AI would have to have some default setting (this is the externalized part) that defines what ratio of different unit types it should strive for. This is further complicated by how many armies the AI will have, but lets just look at the national picture and worry about creating the armies later.

So you would have a weighted list of unit types (could be all units in the game, but that seems like overkill).

So to do this in a simple way...

Militia
LI
LI-ranged
MI
MI-ranged
HI
HI-ranged
Archers (short, long, comp, xbow)
LC
LC-ranged
HC
HC-ranged (does that even exist?)
Flyers (perhaps light and heavy? how many differnet flyers are there outside of caelum)

Aquatics would have a different list, but lets stick to the land for the time being.

So from the above list of units types a check is made to see if the nation even has the posibility to recruit the unit type, followd by the amount of available resources to spend on each unit type. Then some algorythem dependant on other settings (national preferences, AI personalities, counter needs, ...) is applied and the existing %s are modified to new values (or left unchanged as needed). Finally, units are ordered to fit the new %s.

That's how I'd probably approach army compostion anyway. Realize this is only part of the overall package, the location of the units recruitment and the recruitment of commanders would also have to be factored in somehow, but that should happen in another matrix I think, though the matricies should be tied together through the controling algorythem(s) that affect them.