Good idea, with the radar controller the star perhaps, with TCAS and transponders as support
But isn't that the whole point of see and avoid being the last line of defence outside controlled airspace? Aircraft outside controlled airspace are not required to have transponders, nor TCAS, many don't even have electrical systems.
I know you'll say but what about primiary radar.....I'm getting a radar advisory service, but as I understand it many types don't paint very well on primary radar. Primiary radar also gives no altitude indication. Hence the need to have see and avoid, which has only got a chance if the speeds aren't too great, which is why we have a speed limit.
dp