People get caught up in semantics...you are hyperfocusing on the word whistleblower like it has to be a government official but it doesn't. According to Wikipedia a whistleblower is "is a person who exposes any kind of information or activity that is deemed illegal,unethical, or not correct within an organization that is either private or public."

That said, every one of those people listed qualifies. Gordon Cooper stands out as a one of the original Mercury 7 astronauts that has spoken about the landing of a UFO at Edwards Airforce Base that was filmed by Airforce cameramen. He examined the film and sent it up to his superiors. The craft filmed was a saucer, and not any known or classified aircraft. That was 1957 and the government has never stopped keeping the public in the dark about the UFO phenomenon.

The irony about the idea of a credible whistleblower making any impact on public perception is that it wouldn't. Edward Snowden came out with information that the Govt is spying on every American citizen and the public did nothing. Luis Elizinondo came out exposing a government program to study Ufos with a declassified military video to back him up, and a high profile NY Times article and the public did NOTHING.

The only thing that will wake people up is a public UFO landing with live Alien occupants broadcast worldwide. Anything short of that will have little significance towards disclosure.