I agree with the removal or warning shots, but I think the rule should be "You must give a terrorist a voice or text-based warning before killing them if they are violating orders in a non lethal way." I agree with anomo on that one. You shouldn't have to shoot a T if they are, lets say standing near the vent on a three box rule. First, you should say "T, stay three boxes away from vents or you will be killed, This is your warning." Then, if they don't follow that, you can blow their brains out.
If the warning shot rule was removed completely, CT's could massacre T's for just putting one foot out of line. That would make it unfair on T's who didn't hear the orders or do not understand them well.