Why not build 500 armed drones, and keep 100 in the air at all times? If Hamas fires at the drones that is good - they would waste ammo. Meanwhile the drones are up and ready to attack any launch site. These terrorists need several minutes to set up and launch, and they can really only launch from certain open areas - the drone operators can spot the tell tale signs and fire at the terrorists. If they are late, the drones can follow the terrorist cell that fired the missile and attack them. Or heck 3 drones can be sent one to try to hit them before they launch, one just after they launch and one to chase them if the first two miss.
I think there is a good future use for drones in this capacity, effectively building a web like deterrent that is an anti-rocket system and a counter-attack system all at once. Just fly them in random pre-designed pattern over northern Gaza looking for places/people to shoot.
That’s good, too. But it’s reactive. I want the organization taken down once and for all and made an example of. That would be proactive, as would be the first drone in your idea.