I like what Dean Baker said about regulating the financial services sector, he said that Glass-Steagall (or some modified, new version of it) is indispensable for two reasons. One is the fact that there just are not that many lawyers at the SEC and it is difficult to police for, let alone prosecute, the vaguely defined "systemic risk" presented by every firm and every asset. Sometimes, a big and dumb, black and white regulation is the way to go when those whom we regulate are so litigious, unethical, opaque and well connected. The idea is that it is easy to catch and easy to prove that commercial banking deposits are used in investment banking.
That is the legal argument, there is also the economic argument. The growth of shadow banking, high frequency trading, derivatives and other risky, socially useless financial activities has been subsidized by the siphoning of money from commercial banking. If we could choke off the oxygen to speculative finance, there would soon be much less of it to have to regulate.
You are right that there is not one single solution and that Hillary Clinton would still be miles ahead of any Republican. In fact, Ted Cruz was recently boasting that on day one in office he would "suspend" the CFPB. Sometimes, I think of voting third party if Bernie loses the primary and then I hear someone like Ted Cruz speak. The GOP nominee will be Hillary Clinton's best get-out-the-vote surrogate, if she does indeed win this nomination.