If you define "rule-breaker" as "generates invalid blocks", then the only punishment rule-breakers receive is that... their block is invalid, they're ignored, and they get to try again next time.
I don't see any sophisticated collaboration model in play here.
> Even if the Fed required only trusted nodes... Lots of other problems -- everything from medical records to real-estate -- become a lot more tractable.
Why aren't they solved by a database and a public API? What does the blockchain add?
(1), (2), and (3) are true of a system where a single trusted coordinator gets to order (and perhaps reject) transactions. A slightly less anonymous version of any electronic stock exchange would count.
(1), (2), and (3) are true of the Debian apt repository.
(1), (2), and (3) are true of any game without secret information, like chess or Go or Pretty Pretty Princess.
You could call all of these "blockchains," but I think that makes the term so generic as to be useless. If you want a national public ledger, that sounds interesting, but please call it a national public ledger, not a blockchain.
You don't need the distributed consensus or the decentralization or the trustlessness. There are blockchains with central coordinators and without trustlessness that may still prove very useful especially in global finance. People think Bitcoin or Ethereum are complicated but really, they are nothing compared to the global financial system. Distributed blockchain databases are much more elegant than what we have today in terms of achieving consensus on a very large (global) scale.
FedCoin is a crazy idea but it's not stupid. A national public ledger would open a lot of very interesting doors. (Though the republic would likely collapse, see my other comment.) Even if the Fed required only trusted nodes (ie bank-like entities) it still would provide everything from a true national ID system to real, binding peer-2-peer lending between citizens to a system where everybody has perfect, real-time visibility into the national economy (unlike the primitive system we have today where the Fed collects a bunch a data, massages it, and then announces it each month.) Lots of other problems -- everything from medical records to real-estate -- become a lot more tractable.