So, my first question is, if you were going to implement your idea...
How do you stop me from running mining equipment in my house in the U.S.?
How do you stop someone else from running mining equipment in their house in Spain?
How do you enforce your idea so that the Central Banks are the only miners?

If central banks want to be miners, they can already do that.  Nothing is stopping them.  But your idea isn't adding Central Banks as miners, your idea is REMOVING all other miners from the world. What are you going to do, knock on doors and inspect households and shoot anyone that is found to be in possession of mining equipment?

My second question is... How does your idea solve anything? It's still an arms race.  Each central bank will want to have MORE hash power than the other countries. This will both bring in more revenue (to offset their mining costs) AND will ensure that the enemy countries can't collude to attack transactions from allies.  As such, total amount of equipment and electricity will continue to increase.  Only now, instead of the amount of mining being self-regulated by profitability, these countries can tax their citizens and engage in mining at a loss to increase their total influence.  The will result in even MORE electricity being used than the current system.