AI recruitment can be modified somewhat as part of the AI personality setting or whatever it is called. Part of it is economic policy (building) the other is supposed to help determine the relative proportions of unit types in its armies IIRC.

Here are some notes I have copied from someone's posting about this:

Troop personality:
smith - exactly level

mao - biased towards mass troops, light infantry

genghis - biased towards missile cavalry and light cavalry

stalin - biased towards heavy infantry, mass troops and artillery

napoleon - biased towards a mix of light and heavy infantry, light cavalry

henry - biased towards heavy and light cavalry, missile infantry

caesar - biased towards heavy infantry, light cavalry, siege artillery