The heterogenous nature is why I suspect some drugs may work for some people even if it doesn't for the majority. Most drugs probably won't do anything for most of the patients. But you are right, the effect could go either way and you wouldn't know which way ahead of time. At this point however, certain safe drugs making ME/CFS permanently worse is as much (case-by-case) anecdotes as making it better. So it should be left as a matter of belief for each patient to evaluate and decide.And what about the heterogenous nature of the patients - don’t we need to assess the risks on a case by case basis?
There is a certain amount of risk in being overly risk-averse too, at least for the moderate to mild end of the spectrum. If you stick to strictly safe routine, for example, you are not going to discover anything about the personality of your ME/CFS. Some of the discoveries could allow you to better manage your ME/CFS or even improve. What are the chances of that? And What are the chances of making your ME/CFS permanently worse in the process? Each patient will have to decide on their own. I just think it would be nicer to make it easier for those willing to experiment. Who knows, new insights or solution may even emerge through these experiments.