considering the rarity of these types of events, and considering the number of flight made every day, and the few reports of personal near misses,
maybe the cheapest and safest option to combat this problem is an increased awareness of traffic avoidance and radio procedures be placed in the training syllabus, and made a significant point in the BFR process.
it seams to me most incidences are caused by simple radio misuse errors and poor airmanship by not really paying attention to whats going on Outside the window, when you hear a radio call, make it a point to actually visually sight the aircraft making the call.