Agreed--a thoroughgoing, interdisciplinary examination of a small number of cases is likely to yield much more information than a broad-based study. As to potential data, the only quantitative data collected by a true scientifically-designed study that I am aware of is for the Hessdalen Lights. While qualitative data is, by its nature, much less persuasive, it may be the only high-quality data available for many cases and hence is a limitation that researchers have to live with. I do commend Chris O'Brien's attempt to collect high quality data via his camera project and I wish him luck and success.
Best,
Brian
Since photographic evidence has been falsified, even photos taken under controlled conditions will not fill the bill as the hard evidence the field needs.
There's no substitute for high quality medical data about witnesses developed by fully vetted professionals in a clinical setting.
A few cases that are impossible to dismiss as hallucinations, delusions or hypnagogic distortions would advance the field scientifically.
Science is often denigrated by true believers as limited in its vision of anomalous possibilities.
While that is probably accurate (except in describing advanced particle physics and cosmology), a few scientifically unassailable cases would do more than the countless anecdotes now on file.