Sorry , I meant ACAS ,because we currently thinking about if we can make a rule about heading when two aircrafts are gonna to hit each other.
No need to reinvent the wheel -- when to aircraft are on a converging (ie collision, or threat-of-collision) course, the aircraft that has the other aircraft to it's right, shall give way. When two aircraft are approaching head-on, both aircraft shall give way to the right. Let's not forget the basics!
(However, follow the RA and don't pull any stunts!)