@Tchouk
Indeed, scripting can achieve a great deal of results, but in my experience the more scripted behavior the more open the AI is to player exploits.

@SamuraiofDoom
If your talking a player-controlled faction, that depends on how you spend the money, there are no inherent problems with it. However if your talking an AI controlled faction, they would recruit more units then they are capable of maintaining and their economy would crash as a result.