Of course there is: you could attack only battlefield targets, or only strategic military targets, or only one of the enemy's cities. MAD requires two things: first, the technology for mass destruction, second, the geopolitical conditions where either side can credibly threaten complete annihilation if provoked. Nuclear weapons provide the first by themselves, but the second only incidentally: the nuclear powers have come to a credible mutual understanding that they won't use nukes in their various border skirmishes, and that any use of nukes represents an escalation which risks MAD.

World leaders could hypothetically come to the same understanding regarding drones: use them anywhere in the world and you will start a nuclear war.

Yes, except for one big difference that I see: individuals can't go purchasing a nuke like they can a drone. So while the MAD concept works with nukes, because only nation states have them, the same isn't true for drones, where individuals can have an unlimited number, in addition to governments. World leaders can agree re: drones and attacking each other, but that won't stop an intent individual. I think people might be quite surprised what you can do with a consumer grade drone purchased for a few hundred bucks hooked up to lidar, multiple gps sources, swarm technology so they communicate with each other and object recognition. Now just rig up an explosive device, chemical weapons or a gun. You can even drop items (bombs), or pick items up using retractable claws. You can do an awful lot with a consumer/hobby-grade drone hooked up to some cheap sensors using something even as basic as an arduino with open-source software like ArduPilot, which is so advanced (and cool) even Nasa uses it.