The lawyers at the time lied when they said there was secret information. (The Supreme Court declined to look into the matter fifty years later.) And the report acknowledged that there was a major record of negligence on the B-29 and a history of trouble. And United States vs. Reynolds has been used many times to throw out negligence cases.
Now, I think most people believe that the government does have information that had better be kept secret. We could rely on in camera inspections by judges. But who says that judges are the best people to do this. Are they most likely to weigh well the publics right to know vs. legitimate secrets. Are judges the most likely to not leak important information. Dr. Bailey talked about the problems from the Gulf of Tonkin and dishonesty by the government. The State Secrets Protection Act in Congress was introduced twice with no result to require in camera inspections by the judge. The judge coudl require that the plaintiff would have an attorney with appropriate security clearance appointed.
The other possibility is that people be selected whose integrity is impeccable. Individuals like just retiring general McChrystal, Norman Schwartkopf, Congressional Medal of Honor winners. They would review documents and decide which ones should be released or perhaps be the sortition jury to decide to such cases. What a wonderful way of using these individual's talents, integrity and credibility!