Airmann,
On your 2nd point, I have passed opposite direction traffic many times on random tracks.
On your 3rd point quote “how many times have planes collided head on on the same airway?” I think there have already been 2......Learjet/B737 over Brazil, also B737/HS125 over Senegal. If we don’t do something now it’s only a matter of time before hundreds more die needlessly.
We now have GPS and RVSM, these have both conspired to increase the risk of collisions. You won’t find me on any busy centreline.