Thanks for the examples:

acupuncture, meditation, aromatherapy etc. Low-carb diets were denigrated for a long time but they've been shown to work at least as well as other diets

None of these seem to fulfill 3. They seem to fall into the category of somewhat decent with lots of exaggerated claims and enthusiastic followers.

Fecal transplants are a great example, although wikipedia says that most historical fecal therapies were consumed, and I don't know if those work (doubt it). Also it doesn't really fulfill 2 - it was doctors that first pioneered it when it was a weird fringe treatment. And thinking something is weird/extreme and fringe is different than thinking its a crackpot idea. But still a good example.