This is a beautiful dream but i do not think that it can happen every. This will pose a possible threat to the demand of USD and the US would never love that. Yes it can be accepted as secondary currency which will bring ease and you would not have to go to the exchange or bank to convert your currency.

Besides, majority of the countries are in sheer financial crisis and they just cannot pay attention to this new system and might not be able to accept it as a secondary currency because the demand for their already degrading national currency will further decline.