Glass-Steagall was a sensible restriction. If banks want out of Glass-Steagall, then they should also be disqualified from FDIC or bailouts such as we saw under Hank Paulson and his ObaMaoite allies.
Unfortunately, the banks seem to want capitalist profits and socialized losses, and thanks to their lobbying, Glass-Steagall was repealled while Federally guaranteed bailouts remained.
Your proposal makes perfect sense: any bank with Federally guaranteed loans must be subject to Glass-Steagall, and anyone who wants secure deposits can choose to take their business to such a bank. Those banks who want to be exempt from Glass-Steagall will also be exempt from any Federal bailouts if they gamble away their money on high risk securities. Such banks should be required to inform all of their clients that their loans are not Federally guaranteed.