These are necessary but insufficient conditions. A bad trip may be triggered by a fleeting recollection/thought. I believe that a medical procedure cannot be based on such precarious approaches.
I do not known such researches but I agree that it can work for some people, especially for suggestible people or who strongly trust in therapist. But in general we do not be able to control it. Any psy trip is similar to sailing in ocean.
In my opinion the main problem of the using of psilocybin, LSD and other psychedelics in medicine is unpredictable effect that depends on not only the status of a pacient but on entourage too. One time you have a good trip, but next time you get into TRUE HELL.