The biggest problem is finding people that will follow orders when the penalty for not following orders is lower than it is for a military officer or enlistee. That barrier will probably preclude civilian contractors that have never had military service from performing that job. Don't know about former-military civilian contractors though, they might be better at not flinching, but then there's the legality issues surrounding the ramifications of bad calls where innocent people died, or where someone intentionally does something that kills noncombatants. At least in the past civilian contractors had to be present to do the acts that killed innocents such that the country in which the acts were committed could mount something of an objection. What's the law on a civilian remotely operating a machine in a foreign country that's specifically equipped to kill, using that machine to kill? At least a military member could see prosecution if through the military system of justice, but I don't know how well that would work for civilians.