What an interesting idea.
I suppose there should be a be big bold preface to begin with.
Please do not take mental health advice from an internet forum, if you have serious issues you need to work on, please do so under the guidance of a trained professional.With that out of the way, I really think this idea of self-directed psychedelic therapy is an interesting one. Assuming that is what you are getting at, that's what I got out of your question, apologies of that is not what you intended. In a perfect world we could all have access to a psychedelic friendly therapist, but in the absence of such an open minded professional I do think a lot of work could still be done.
The exact methodology would have be custom tailored to the individual and exactly what they want to work on and of course having previous experience in therapy would be quite helpful. However, it wouldn't be too difficult to create a self-directed program. For example lets say you have a behavior you want to work on, drinking too much or smoking or something like this. It would be fairly easy to download a manual on cognitive behavioral therapy and create a plan for yourself then work on some of the various exercises under the influence of say psilocybin or whatever substance and attempt to modify that behavior. Or if you have some trauma you want to face you could create an outline for your personal process from a manual on PTSD treatment and attempt to work through that trauma under the influence of mdma.
If one were to attempt this route I would highly highly suggest checking in with a therapist from time to time, even if you don't mention your personal work, just to get some professional input and should anything go awry, it couldn't hurt to have someone who is trained in this area to call. This is tricky territory indeed but I could see such a program being of quite a bit of benefit for a dedicated individual.