This is actually a very good idea, but I am sure NIST, CIA, Homeland Security,... will claim all the evidence stored in the blockchain to be false or unreliable. The fog they have created around this totally impossible collapse of 3 buildings "due to office fires" is so big, that it is almost a mission impossible to get a correct investagion, especially 16 years after the event.
I hope we will know the truth someday, but my gut feeling says it won't happen. Hive account@corbettreport made the best "speed" documentary there ever was made about 9/11 in this video, it's funny but scary as hell, and I still get the shivers when I watch it...