One way to approach it would be to organize the data around the questions "What seems to have an effect on the system? What makes things better, what makes things worse, even if the effect is very small (but reproducible)?" Then, investigate those things.

Doctors are kind of terrible at doing that. They tend to have a tool box of "these are the things I know how to do" and any information that doesn't fit their specific specialty is discarded as irrelevant.

I'm not sure how useful it would be to weight things by evidence if part of the problem is that some things haven't been investigated enough, or are simply not well-enough understood by modern medicine and science.