No, not really. You could have a script running either for each enemy unit or looping through all enemy units, that calculates the distance between all enemy and all friendly units, and whether one unit is facing another, and then reveal the unit. For either a large number of enemies, or a large number of friendlies, this would probably cause an unacceptable amount of lag. It also would not be able to tell when one unit has a clear line of sight to the other.
If was possible, someone would have done it by now. Instead I suggest turning up the enemy skill to full, and giving the enemy HD weapons/ammo.