To be honest, I don't think we should be seeking monetary settlements in cases like these, but rather criminal prosecution.

Large settlements are about as good at deterring cops from committing crimes as they are at deterring bankers from committing fraud in the name of the bank, because in either case the "principal" -- person paying the penalty -- is neither the cop nor the banker. Police departments don't care because the money is coming from the taxpayers and not the cops. The banks don't care, because the fine they pay for the fraud is less than the profit taken by the fraud.