Without operating nose gear, eventually that nose will touch the ground and you will lose all control of direction. I'm not sure what that speed is for the A-10 but for the planes that I fly, gear-up is a better option. At least you're sliding flat, not with your nose digging into the runway.
I don't think the operator could see it at 3000ft. I fly unlimited class RC sailplanes in the 14 to 16 ft wingspan size and they are mighty small at 3000. And, yes, I do have telemetry.
A good idea but it will only work if the drone pilot is actually in control of the drone. A lot of times they are on internal guidance by GPS and the pilot only takes control when it is back in the area he launched from.
This guy has just assured that no one will ever be able to do that again. They'll be using a different aircraft or it will be painted in some other colors, fly at night, something. The Secret Service pays attention to stuff like this.
Much more difficult than you think. I fly combat with radio controlled aircraft. We often fly a complete round without even a single "cut" and we are each towing 30ft streamers. And, that's with 10 aircraft per round.
Most drones are built by the owners from readily available parts. Motors, props, available anywhere. 3D print a frame. Buy or breadboard your own electronics. You could only mandate manufacturers to add transponders.