Your Requirements: 1. Have the weight of every passenger while not uniquely identifying them.
2. Have the aggregate weight of all passengers on the plane
3. Have it independently verifiable
4. Trust that no additional data has been siphoned off.
What you proposed says that everyone step on a scale to be weighed. At this point #4 can be easily broken. Any company can easily split the data, send on through your complicated block chain system and send a copy to their on private DB. They've still captured the private info you wanted to not be private. A blockchain did nothing to solve this.
Ok so the solution: make this scale opensource and ensure via some signing method that the software scanning tickets and managing the scale are running this open source visually verified code. Fine that solve the problem because everyone can inspect the code and see what it's doing. So what's the next step? Write code that simply takes those numbers and sums them together and outputs the sum! Everyone can see that no privacy is being violated because they can see the code running on the scale. And they can see that it has no negative privacy implications it's simply an anonymous sum.
A blockchain to the solution I just discussed provides no value to this. It's not solving a problem that is present here. Signed & verified open sourced software is what's required.
Whereas I'm coming form a position in which a middle ground can be met by all participants given the parameters; gathering what is deemed 'useful information' while understanding that it can and has been misused continuously to create a vastly dystopic industry that relies on such practices.
So to counteract said potential problem do so with the least amount of identifiable variables in the equation and have privacy an absolute.
Again, you can discount the need for privacy all you want; the FAANG types usually do and make billions from it: that's the playbook until you're sitting a testimony in front of congress (mainly for theatrics) and another billion dollar fine for misuse of private information.
> Use blockchain to solve problems that have requirements around the value it provides.
Agreed, which is why I referenced the voting usecase and how that would be a more apt use of this solution.
To put this into context, I think of your argument as: Why are you asking for these silly seatbelts and these overly complicated airbag balloons into this design, we were just asked for a box with 4 wheels!