general,
that is a good question and one worth investigating
i've had trouble in the past trying to plug in civ-specific armies that are spawned only (ie can't be built). i realized that the 'build army' unit set in the editor precluded me from plugging in these civ-specific units...but to try the culture entry would be worth a shot imho.
here's my basic take on army units in civ3 --
armies in civ3 are a strange thing imo. by this i mean that they can be game breakers in terms of balance, especially for the human player (this is why i never have them able to be built in any of my projects, too powerful and exploitative for the human). of course, this is only one man's opinion...but in my time of civ3, i've come to find that there are some defficiencies w/ the default setup of the army units.
my first observation about the ineffectiveness of armies was discovered when we were developing TCW back in '05. I_batman always used to point out to us how crappy the AI would be w/ its armies and especially how it loaded them up. it would put the strangest of units into these precious army units and we would all be like WTH? so this led us to restrict which units could go into the army units (via the 'foot unit' flag). this went a real long way for us in terms of cajoling the AI into actually loading decent units into their armies.
piggybacking off of this method, i took it another step w/ TCW 50s. we resticted which units could go into the armies and we had them available only through the GLs. spawning armies via the 'battle created unit' is not good as the game engine is set up to never spawn another 'battle created unit' again until that first one is 'expended'...now, by 'expended', i mean that it has to either be killed off, disbanded, or 'cashed in' for --as per default civ3-- an army unit or to rush a wonder/building. my civ friend MarineCorps was the one who originally pointed this out to me a few years back and it was quite a revelation

anyhow, knowing this, i've reverted back to this default civ3 setup for all of my projects (although AoI v3.0 did not have this arrangement - it was discovered after it was published).
the last major point regarding the armies is to chop down its transport capacity to only one. now, this sounds crazy...but read me out

we ramp up the HP value of the actual army unit. it is normally the equivelent of three infantry units (each inf = roughly a division and the army unit = roughly a corps).
i can write w/ great enthusiasm that the above setup has worked marvelously. the AI gets these army units are about the same rate as the human, it loads the same types of units into them, and it has roughly the same strength as ones loaded up by a human. and to cap it off, we've seem outstanding AI useage of the army units once we implemented all of these changes (TCW 50s). there were a few times when i saw an enemy army unit baring down on my cities and i was truly terrified. when was the last time we could all say that?
