A general ring-fencing requirement, separating out retail banking, would mean a profound restructure of the industry the Australian Bankers Association said.Murray's panel mooted this idea as something needing study, like every other topic mentioned.Sorting out a 'too big to fail' method requires "a deeper understanding of what it means and what might be done about it.," the ABA said.Banks are expected to have a range of views on the issue.COBA CEO Louise Petschler said the mutual sector was "disappointed that the interim report makes no attempt to estimate the size of the funding cost advantage enjoyed by major banks due to the perception of being too big to fail."The FSI panel has ducked the issue by saying any funding cost advantage is likely to fluctuate over time and could be transient if Government policies effectively reduce the systemic risks posed by larger banks. "This contrasts with the International Monetary Fund's April 2014 Global Stability Report finding that implicit subsidies enjoyed by systemically important banks are 'large'."Australia should impose a temporary levy on the four systemically important banks, Petschler said.The IMF estimates these implicit subsidies are worth at least 15 or so basis points in the United States, 25-60 bps in Japan, 20-60 bps in the UK, and 60-90 bps in the euro zone, COBA said."The FSI panel has been too hasty in distancing itself from the levy idea," Petschler said.