Try using a twist on Glass-Steagall. Bankster's gambling is no different from Casino gambling except for the terms used.
Derivatives and Future options are no different than sports bets and table game betting
Banksters try to rig the games by buying off the referees (rating agencies) and compromising the players with mortgage fraud just like in the gambling field.
The difference is, it is well accepted that Casino gambling is a mental illness, an addiction, that requires treatment and Bankster's gambling is a Capitalist dream (IMO a nightmare)
When you bring down the American economy with gambling greed and addiction, these are not sane people. These people need mental help to merge with society, not ruin it.
So my message to Bernie, in these primaries, is not only to break-up the banks but profess and treat the people in the banks for the mental disturbances they possess.