Why not keep it simple? No bells or whistles, just an off the shelf TCAS would have prevented this accident, and would cover most other situations, with the exceptions of military formations and dynamic manoeuvres when the answer is probably to switch off all or some of the alerts.
An off the shelf TCAS was available in 1991, but rejected as being unsuitable for FJ. Now, 23 years latter, we have decided to fit it (I think).
DV