Radar advisories a good idea
Gums is correct, using ATS radar advisories for traffic is certainly a good idea, as well as using all available tools, such as the F16's radar. But if the C150 pilot requested advisories and was rejected (e.g., happens sometimes, especially with requests for Class B transits), or feared being issued a massively circuitous and sometime dangerous route (which also happens sometimes in Class C or B, as for re-routes over open water at low altitude in an ASEL airplane), then it underscores the point that the present ATS system is still seriously obsolete, if not broken, and needs reconsideration and re-design. Regardless, the fully allocated cost of providing such radar advisories to the C150 in the present ATS is very high, and for the most part is economically indistinguishable from IFR IMC ATS ops costs. So for the long run these separation service costs need to be reduced by at least an order of magnitude. That said, any cost, regardless of how high, would have likely been better than the outcome in this case, for both the C150 and the F16. All three victims deserve our support in this case, the C150 occupants, the ATS specialist, as well as the F16 pilot, at least until all the facts are independently established and verified.