This has in fact been simulated in a dense traffic environment some years ago and the surprising result was the small number of conflicts when everyone just flew direct to their destination (Free Flight) while being able to see all traffic. No I don't have the URL to hand.
Folks,
Such studies have been done over the years, the first one, of which I am aware, was financed by United Airlines, with a major US university, in the 1960s.
Each one I have read came to the same conclusion about en-route (not terminal) operations ---- that the joke definition of ATC was correct:
"Air traffic control is a system for concentrating a small number of aircraft, in a vast and empty sky, over one point, greatly increasing the collision risk, and thereby justifying the need for air traffic control".
Then and now there is a truth in this, the first study was long before even the first rudimentary TCAS, random tracking produced a lower collision risk than organised ATC.
Tootle pip!!