I think something like that has merit. You never know whats going to happen and where, and you may very well be dealing with non combatants freaking out and doing who knows what, if something should go down, especially in a crowded venue.
In the split second you have to decide, do you shoot the boy running at you with a dark 12 oz pop bottle pointed at you, or the boy just to the right with the gun?
May also help you to deal with using one arm to deal with or move the non combatants out of the way so you can shoot.
"If the rule you followed brought you to this,
of what use was the rule?"
“The enemy is anybody who's going to get you killed, no matter which side he is on.” - Joseph Heller