IF you are referring to UAVs, the key is not the drone, but the weapon systems and surveillance payloads they deploy. The US Predator drone, running off a small commercial engine, is nearly invulnerable to ground fire because the Hellfire Missile and the USA's unsurpassed surveillance gear allow it to loiter far above enemy weapon systems.
The Turkish Baykar Bayraktar TB2 has seen considerable combat service, most notable in Syria and the Ukraine. It operates at lower altitudes than the Predator due to the limitations of its sensor and weapons, but it has racked up impressive combat results in comparison to the number of drones shot down.
You won't need many rules for drones, since shooting them down should be beyond PC resources. They will inevitably be 'off the map' resources. However, while the airframe and power pack are fairly simple, the avionics, sensor payload, and weapon systems are very high tech, and will require massive infrastructure to produce, unless this is 'legacy gear'. Not to mention very skilled flight crew and a hefty load of infrastructure to use.
