Better PR isn't going to mollify an investing public that no longer believes the equity markets are fair to investors. Wall Street has pushed its advantage in asymmetric information so far that the people on the other side of its trades don't want to play anymore. No one is going to believe a news release stating "Wall Street wants to try harder" after an avalanche of stories on how Wall Street has picked investors' pockets. No investor is going to trust Wall Street until senior executives who commit fraud - especially those at MF Global - are prosecuted.
Here's a good analogy. A senior U.S. military official once remarked that the key to convincing Afghans that the U.S. is on their side is to "worry a lot less about how to communicate our actions and much more about what our actions communicate." Wall Street should worry less about how to spin its behavior during the 2008 financial crisis than about what it should do to remove anti-client conflicts of interest.