Buzzbombs!
Perk them
Have 5-6 launch a few seconds apart during each perked salvo
Have them randomly hit within 1/9 of a grid:
i.e.: I selected 5,6, keypad 5: they would all land in that 1/9 of a grid square.
Have a time limit between salvos fired at the same coordinates.
The launch sites would also give us more targets.