I kind of like the idea of VISA/MasterCard/Paypal/Bank of x
They are public companies, they have a reputation to protect, people can get fired if it all hits the fan. If Visa had constantly poor security, all their customers would leave for Master Card.
If the Govt controls the payments system, and the payments systems is fragile, or easily corruptible, you can't just dump them and go to the competition.
At least in my country, govt employees pretty much need to shoot someone (during office hours, and in the office) to get fired.
Nothing good can come of this.