George Dorgan from snbchf.ch recently laid out his thoughts on why the biggest ever proceeded monetary experiment in Japan could work out. People following this, might want to dig into this elaborate article. He goes ahead saying an exchange rate target could be put in place to fight volatility in the USD/JPN currency pair if needed:
Introduce an exchange rate target and maintain stability!
The Japanese public wants stability: the best way to achieve this is to clearly announce an exchange rate target of 90, to which markets could commit.