qassam can easily be modified to change direction.....add a couple of fins that change their axis once every 10 seconds....they can powered by a coil and a spring ...not a big deal
And thus completly missing the point of murdering civilians. If you change direction - you change destination. Take into consideration that there arent that many people living in the southern parts of Israel. Its already a longshot if you fire from gaza and actually hit anything with a cheap rocket, launching a cheap rocket that swirrles and dances in the air will be pure waste.
Though one could always argue that they will develop a spin&rotate system that will be GPS guided but...... Iron dome can counter that too.
Only way to counter the system will be launching a massive barrage that will justify Israeli aggression. Basicly its a dead end for Hamas.