Never been done

The uncertain future of central bank independence 

In a democratic society, independence for the central bank can be justified only if actions are limited to fulfilling a specific mandate. 

In USA we run the standard codependent central banking we always done, just used different tech.  We also run lots of private currency, unobservable by central bankas. 

Central bank money us always good for government goods at the stated price, they guarantee it else they legally allow gov devaluation.  That is the definition, the rest of the discussion is about faking it.