Patients (and i will speak for most of us) want proof of illness on paper. Because no one believes us including drs, employers, insurance companies and family members.
If looking at the research for ME/CFS, I think there's already pretty conclusive proof of biological illness, even if the actual pathology isn't understood yet. OI in ME patients has been pretty well documented for at least a couple decades now, and I don't think that anyone has ever tried to claim that swollen lymph nodes can be caused by psychological factors. This hasn't translated to a quick and easy blood test, but it really shouldn't have to.
The bigger issue is that certain groups have latched onto a psychogenic explanation and are 100% invested in it for various reasons. Insurance companies save a lot of money with the psychosomatic explanation. Governments avoid looking incompetent and/or responsible when ME/CFS is explained as being our own fault. BPS clinicians protect their reputations and careers by refusing to accept alternative explanations.
So on an individual basis, ME/CFS patients are trying to convince certain people of a biological cause for our disability when no amount or quality evidence would EVER get those people to acknowledge it. The only thing that will cause a change is when those insurance companies, governments, BPS clinicians, and others are no longer allowed to express such a view point regarding ME/CFS. They will have to be told that is no longer acceptable to treat the disease as imaginary or self-inflicted.
That would be easier if the governments were on our side, but most governments are already invested in being on the other side of the issue. If governments are going to change their attitude, it's going to require a certain amount of public outcry. And that public outcry is more likely to result when ME/CFS is better understood, and there's more rigorous research indicating a biological pathology.
So I don't think the solution is going to be every patient getting lab results showing some abnormality or another. I think progress is going to come from large and thoughtful studies which make very nice headlines for the general public, and which even the most ardent ME/CFS-denialist can't convincingly fault. With the lack of government support, those studies are not going to be easy to come by, but there has been a lot of progress lately with crowd-sourcing.