I have been experimenting with this and I wanna make it as easy as possible.
Making units shout and scream custom voices randomly is very easy to do, but the difficulty is WHEN, in what situation do they say something?
Some ideas :
When a unit throws a grenade, you can make him shout "grenaaaadde!!!" or " fire in the hole!!", just add a EH "fired", check if it's a grenade or not, then make him shout (maybe with a possibility of 50%)
An EH "hit" can be used for the "aaargh" & "I'm hit" sounds...
Other ideas?
btw : Does OFP create serious lag when you add one or more) EH for non-playable unit on the map?