First, let the all country governments will accept this Bitcoin as legal currency later we can think about this topic. Yes, this is good idea I agree, but this will not work out in real time. Except for few country now Bitcoin is illegal in all country. If there is no income from BTC, then no govt will accept this as legal. So your idea wants to be execute means it will take a long time.
Yes it is a good idea and we all will love this idea because we all using bitcoins and like to more and more stores start to accept bitcoin as a bitcoin.
But our opinion doesnt matter because we cannot do something about it,because it depends upon the popularity of bitcoins and its acceptance by the government and more peoples across the world.