Here's the problem with suppressive fire: it is worthless unless the enemy you are trying to suppress actually reacts to it. And since the AI doesn't react to bullets flying around them, other than just laying down, there is no reason to even use suppressive fire. It works better to just shoot to kill instead.
Even if you did script the AI to take cover when under fire, it would only be useful in very specific locations: such as when they are near buildings, or behind fortifications. But 90% of the terrain in OFP does NOT suit itself to taking cover. In OFP, any part of terrain that does not have a bush or tree on it is devoid of any cover. In the real world, even "open" fields have small ditches, patches of grass, rocks, depressions, and other micro-terrain. The fields of OFP have about as much of this cover as an empty parking lot.
For example, imagine if you were walking in a huge, empty parking lot, gun in hand, when suddenly somebody 100 meters away from you started firing a machine gun at you ("suppressive fire"). Would you (a) lay down and fire back at the a-hole, like the AI in OFP; or would you (b) allow yourself to be "suppressed", and not fire back?