Large warheads like Kornet cannot be mounted on the small multi-rotor drones currently used by Hezbollah, as they are too large and heavy for small-class multi-rotors to carry. However, if medium-to-large class multi-rotors such as hexa or octa-copters are used, the situation would be different.
It appears only a matter of time before Hezbollah moves to larger multi-rotors with greater payload capacity. Larger drones mean greater payload, which means the ability to mount larger warheads, resulting in deeper penetration and higher effectiveness. Until now, Israeli armor has largely survived Hezbollah's multi-rotor attacks thanks to the design and armor protection of vehicles like the Merkava, but this advantage is gradually diminishing and will eventually disappear.
Israel cannot rely on Merkava armor protection indefinitely. A point will come when armor protection, especially on the top surfaces of vehicles, will no longer be sufficient to prevent penetration by new warheads — and these will not necessarily be limited to weapons like the PG-7.