drone swarm forming wall to intercept missiles

many cheap drones simultaneously launched, 

drones form a drone swarm, 

drone swarm form a wall in the air to intercept incoming missiles 

civilian commercially available drones could be used, 

system would be cheap, 

high availability of civilian commercial drones, 

little space would be needed for system, 

drones could be easily replaced when destroyed 

since system could be considered harmless, 

system could be used in a variety of environments