Being a pilot, I am quite familiar with all of these systems. My concern is not about some hyperbolic remote control scenario but rather that the ability to paint targets on a traffic system is sufficient to greatly decrease the safety of a flight. Your "at best" scenario is lacking in several ways. It assumes visual conditions and a target at sufficient distance to elicit communication as the first step. If my traffic system paints a target at my 12 o'clock and closing fast I will aviate before I communicate. This is true in any meteorological condition but doubly so in IMC. High performance collision avoidance maneuvers greatly increase the risks associated with flight. We train for them but that does not make us immune to introducing high wing loads or overcontrolling in an emergency scenarioin the real world.

Incorrect. ADS-B has two components, FIS-B for weather and TIS-B for traffic. If you spoof airplanes via ADS-B you can trigger the exact same kinds of collision avoidance alerts and pilot reactions as a spoofed TCAS. http://en.wikipedia.org/wiki/Automatic_dependent_surveillance-broadcast#Traffic_information_services-broadcast_.28TIS-B.29

I really hope you are a developer. I make all of my money salvaging projects after they have been in the hands of people that do not understand the relationship between computer science and quality programming. And business is booming.