What would have been the value of such a study? Would it really have accomplished anything?
To begin with, a one-time study could not be expected to conclusively prove or disprove molecular nanotechnology manufacturing (although it's possible to think of several things that might send supporters back to the drawing board discredited). But many scientists have apparently taken the current low opinion of molecular manufacturing to mean that it's already been discredited or even disproved. A rigorous study that failed to disprove molecular manufacturing (failed to find a showstopper) would surprise a lot of scientists—and surprising a scientist is always worth doing.
A study could also settle some important open questions and clarify others. For example, a study might go through Eric Drexler's Nanosystems with a fine-toothed comb looking for errors. There seem to be no significant errors in Nanosystems; we've repeatedly asked groups of skeptics to point out Nanosystems errors and no one has done so. Is Drexler really that good, or is it just that the book has never been adequately criticized? A one-time study could answer that question. And it's an important question, because if Nanosystems works, then nanofactories probably also work. And if Nanosystems doesn't work, the field has some serious rethinking to do. (Though nucleic acid engineering looks like a good runner-up technology.)
A study could show which positions, on both sides, are based on consensus or unwarranted extrapolation rather than evidence, and force us all to focus on the actual research. A lot of today's discussion about molecular manufacturing is not scientific. Skeptics frequently make blanket assertions based on hastily formed opinion. Many are simply unaware of the last decade of literature in the field.
At present there is no well-defined field of molecular manufacturing, but there ought to be; enough work has been done already to build a chain of theory and nucleate a field. Simply collating the molecular nanotechnology theory and cataloging its data and arguments in a format accessible to scientists would be a great advance.
Of course, if molecular manufacturing was proven impossible, then Drexlerian gray goo also would be impossible—and proof of that would be worth many millions of dollars to companies in the NanoBusiness Alliance. If they were really convinced that a serious study would disprove molecular manufacturing, they should have welcomed it. Why didn't they?
A one-time study could accomplish quite a lot in a variety of ways. Even if it didn't directly advance science, it would at least clear the air and advance the debate to a point where science could be done.