1. Decentralized ledger.
2. Open source code.
3. The inability of any entity to have greater access.
Such a coin would be a Frankenstein monster that the banks could not control. It may just come back to hurt them. And how are they going to make money from this system? Who is paying for all the infrastructure? And why would I use a banks coins when I could have universal money that works in any country?
I totally agree with this opinion. Banks will not develop their own crypto because they cannot manipulate crypto at their own free will. It's way too transparent.
It's not only about manipulation, it's about the profit, that is the main mechanism that stimulans banks. At their current estimation their own coins wouldn't be supported at the market by the users and wouldn't give them profit. In fact the impact might be just the opposite so banks will not decide to go into such adventure.