Sorry but this is not a new idea but close what China did for twenty years. For most of the PRC's history, Chinese currency was usable only in China with exchange rates closely controlled. Even today the currency is not fully convertible. Starting in the nineties, this situation worked well for them until things got so unbalanced that we have ... well, the situation that we have today.
I believe you missed my point which was that people do not speculate that the Renminbi might be replaced by the US dollar. And that this might happen because it would retain the currency controls presently afforded by the yuan being distinct from the external currency (RMB).
That -is- new, but unlikely for the reason I gave.
