I think any credible experiment must relate to the original phenomena in question. Can people use dowsing rods to accurately detect buried lines or objects?.
That has been tested.
For instance, experiments have been done involving burying lots of pipes in an area of ground, then filling one of the pipes with water. Dowsers who claimed they (or their rods) could find water in pipes underground were then tested to see whether they could accurately find the buried pipe with the water in it. Enough data was collected to make the analysis statistically significant. It was found that the dowsers couldn't do what they claimed they could do, for this specific claim.
From my research most prior studies were inaccurate, biased and outside the context of what was actually being studied. Most past experiments were set up to look for a nonsensical "psychic phenomena" not a subconscious reaction (ideomotor effect) to the surrounding environment. In effect, they designed the experiments to fail by introducing unnecessary elements they knew would probably fail which is clearly biased.
In the test I just described to you, no questions were asked about how the dowsing was supposed to work. Whether it was by psychic energy, subconscious cues, a magical field of a dowsing rod, or whatever was irrelevant. All the dowsers were asked to do was to demonstrate they could do what they said they could do. Turned out they couldn't, which makes an investigation the particular mechanism by which dowsing
might work irrelevant.
Curiously, many dowsers claim that their psychic energies are mysteriously damped whenever they are subjected to a controlled scientific test of their ability. It might be bad psychic vibes from the skeptical investigators, perhaps. Funny, that.
For example, it's well know hunter/trackers can track animals for miles from the smallest environmental details 99% of other people are completely oblivious to. Should we deem the tracker a psychic and test there physic abilities?
This could be tested. For example, if we were to blindfold the tracker, that should not dampen any psychic ability to track, right? If it turns out that trackers can still track accurately while blindfolded, then I guess psychic power remains an open possibility. If, on the other hand, they can't, then it seems very likely that tracking accurately relies to some degree on being able to see things in the environment. Do you agree?
Maybe we could put the animals in closed containers and then have the tracker guess which one contains an animal. It sounds completely absurd yet this is exactly what many supposed dowsing studies did in the past.
In the studies I am aware of, such as the one mentioned above, the dowsers were allowed to go about their dowsing in exactly the way they normally would, with all of the equipment they said they required. Also, importantly, they were asked in advance of doing the experiment about whether they thought anything in the setup of the test would prevent their abilities from operating as they normally would. Any complaints or objections as to the conditions of the test were dealt with by making suitable modifications to the test protocol, until both testers and dowsers were confident the test was fair.
Maybe you've been reading about have been low-quality ones. Probably bad luck for happening to stumble across poorly designed studies. I assure you, there have been many well designed ones.
In any credible dowsing experiment were trying to measure the dowsing wire motion relative to the position of known/unknown buried targets. Who the dowser is, there opinions or beliefs have nothing to do with it. Most people like to confuse an issue with there own biases which is why they need to be removed from the equation. Were simply measuring the dowsing wire motion relative to a target then correlating the data to determine how accurate the process is.
The test I mentioned did all the things you suggest. Skeptical investigators did not choose which pipe would contain water, for instance and did not communicate with the dowsers during the test. The kinds of biases you are worried about were avoided. All the dowsers had to do was to perform as they said they could, under conditions they agreed were fair.