China has suggested the adoption of a single global reserve currency citing the dangers of relying upon one national currency (US$). The currency would be underwritten by the IMF.
It would certainly be helpful to move towards a more balanced global currency regime. The euro is a step in this direction because it is weighted by a number of large economies.
A single Asian currency has been mooted for some years, one of its underpinning rationales being monetary integration.
A single global currency would be a big step towards the inevitable emergence of energy becoming the single currency of humanity allowing integration with the biosphere.
See BBC China suggests switch from dollar.
See People’s Bank of China essays Reform International Financial Regulatory Framework: A Few Remarks (pdf here) and Reform the International Monetary System.