Interesting idea.

Not sure about needing a trading post though – as presumably there would be a federated identity system.

Citizens who transact primarily in a mall town in Seattle should be able to use their same devices and IDs when they go visit (or move) to a mall town in Miami or Buenos Aires.

Alternatively – instead of having a single block chain per mall town (which is more of an anarchical city state type implementation), you could have a blockchain per “industry”. For instance: a blockchain used for health care; another for usage of transport systems, and so on.