I disagree. It's legal in Peru, where all of the cases I listed occurred. (Technically, it's a gray area where, in the case of indigenous practitioners working on foreign guests, the law literally has nothing to say — neither legal nor illegal, but tolerated because tourism dollars. Indigenous folks treating indigenous folks is black-letter legal, and protected.) It's not prohibition, but rather greed and predation, that create most of the harms that have happened in ayahuasca practice in the jungle.
I've never done it, but I have a strong sense that pharmahuasca would be cold, sterile, and missing some of the je ne sais quoi that the "shaman piss" [1] experience offers. I'm sure it would still be a valuable experience, and one I'd be open to exploring, but drinking trees works well enough for me, thanks.
I mean, sure you can puke (I often do, sometimes several times in the course of a night), and it tastes horrible, and your sweat smells like tree bark at the end of the night — let alone the end of the week. That's just the process, though, and "optimizing" it out would probably also remove many of the things that are actually among the most valuable (for me, and everyone else who does this more than once with whom I've spoken) aspects.
EDIT: footnote added.
[1] Interestingly, in one of the earliest-documented shamanic traditions, tribes on the Siberian steppe would use amanita muscaria mushrooms, which are visionary, but also mildly toxic. The shaman would take a shaman-sized dose, and journey, then collect his urine (which still contains threshold doses of psychoactive metabolites), and serve that to his "patients".