Well, I'd love to be wrong about this and hope that you are right. What worries me is that key parts of the technology, like the processor, sensors and software might be available cheaply due to their civilian uses. Manufacturing ability could well be scarce, but these weapons could pass through illicit distribution networks which today distribute machine guns and rocket launchers. I didn't fully understand your postscript, but regarding visibilty, I admit I dont know much here - for instance, how small of drone would be realistically possible for a non-state producer. But I dont see a clear knockdown argument, given that drones are used effectively today. Again, I hope you are right and that there are more technical obstacles out there.