What's the problem?
All CAsA need to do to fix this issue is mandate that ALL aircraft be fitted with ADS-B IN and OUT, plus TCAS, all aircraft with two or more seats must be multi-crewed to help see-and-avoid. Stricter medicals to test hearing deficiency and eye-sight must be 20/20 or better. ALL equipment tested every 3 months. Oh and for good measure any aircraft that has done over 1000 hours must be rebuilt back to "as new". This should pretty much reduce the GA fleet to zero so that the only aircraft flying will be military or airlines. Problem solved!