In Saddam world, there is nothing for defensive purposes, it is only for aggression.
Do you believe that Saddam would have waited for the Iranians to ave Chemical Weapons and he does not? He understand very well that Chemical Weapons are what saved his regime in the Iraq-Iran war, and that is why he was always obsessed in having them.
I don't disagree that Saddam was always trying to build up his weaponry and capabilities. Would you concede that he might also be looking at how he would respond if Iram used nerve gas and how he might protect his forces in such a scenario?