dang dude that'd be kinda hard to make the chaff script, and considering that you RARELY see the missile (missile smoke trails are horribly innacurate in ofp) you only havea chance of seeing the missile in night.
for the flashbang, youd have to do it with an addon, just make it grenade that doesnt have a kill radius???, and than when it detonates, every ai within 20-25 feet of it gets its auto-targeting ai take away, therefore it acts as if its blind and cant see you. you could make it fire at some object to similate the tango firing out of panic. you could also use the whiteout efect to simulate yourself going blind fromt eh flash, and you could play a "ringing" sound.