On the issue of banking, Weill said regulators should help strengthen the financial industry and get banks to follow the rules rather than be adversaries of the companies they oversee.
Case in point, the latest stress test results embarrassed Citigroup CEO Michael Corbat, who was blindsided by news the bank failed the test while he was out of the country, Weill said.
Regarding Dimon's handling of JPMorgan during this litigious environment, Weill said: "I think he's being shot at by everybody. He was too successful."
But Weill didn't fault Dimon for the bank's $13 billion settlement with federal and state authorities to resolve allegations of sales of shoddy mortgage securities by Bear Stearns and Washington Mutual, which JPMorgan purchased during the 2008 financial crisis at the behest of the government and the Federal Reserve.
"You can't fight the government," Weill said. "I think Jamie did a great job managing JPMorgan through the [2008 financial] crisis. He bought two companies that helped the country."
In a 2012 interview on CNBC, the man who invented the financial supermarket called for the breakup of big banks. But a year later, he told CNBC that big institutions don't have to be split if the "right regulation" is in place.
On Wednesday, Weill said: "The model of having a broad-based institution is still a good one," provided the government doesn't keep second-guessing the way banks do business and how much they pay their leaders.