Immidiately after any of the examples you provide, the percentage of barter transactions tends to go way up. There tends to be less use for actual money, and more use for tangible goods used to survive, such as food, fuel, and water.
I don't think any kind of "mesh" network is going to work very well when there are many users involved, or when it needs to cover the entire globe (or even large parts of the world). A mesh network greatly increases the chances of a Sybil attack and makes detecting such an attack much more difficult. There are also privacy implications to using radios to use bitcoin, as it would become trivial for anyone in your area to know you are using bitcoin; this is compared to only your ISP knowing you are using bitcoin currently.
I agree with you about the barter part - but I think it's safe to assume that the levels of barter use go significantly up in these kind of events specifically due to the instant distrust in fiat/banking system. If Bitcoin was there to be used
even fully offline, this would change.
Why do you think people start to distrust the banking system after a natural disaster? I would argue that barter transactions increase because people have less use for anything that can be described as a store of value -- people need actual goods/services that allow them to survive.
About the security & privacy of such an idea, I don't know much so thanks for underlining these issues. It's definitely not the most reliable thing, although perhaps there is one key solution we just haven't thought about yet.
If you are in a rural or even a suburban area, with a mesh network, it would take a very small number of dishonest nodes to pull off a Sybil attack that affects a large portion of the entire network, as
all traffic is flowing through so few nodes. There is little reason to run a node in a sparsely populated area because it will connect to so few people.
We currently have Blockstream's Satellite
In many ways, this is centralized because the satellite is owned by a company (located in US!) and they can decide what services they provide and to whom.
My understanding is that the blockstream satellite will broadcast transactions to anyone whose "antenna" is pointed in the appropriate direction, and has no way of discriminating against a specific user.
Using a blockstream satellite alone will not allow someone to broadcast a transaction, which would be important in a power/internet outage.