blockchain technology are nothing without decentralization, the whole point of blockchain isn't just a digital ledger, i would say to the banks, thanks but no thanks, you can take your centralized blockchain and turn back to fiat
bitcoin is still preferably, no point in making a bad copy of it
I dont think they would centralize it, but they would definitely make some complicated derivative out of it, which would be so complicately coded, that normal peer-review would not detect it, and so they could hide a ponzi scheme in it.
Besides they would instamine it and keep 99% of it between themselves, or just make it with no fixed supply, and a voting system when to issue more of it.
So they would do the same thing as now, but with a decentralized system, which is a bit shadily implemented and contructed, to have a bitcoin appeal to it, when in fact it would be a scam.
so in the end we will just have a standard altcoin like the one in the altcoin section, but made instead from banks, which are worse than a malicious dev
i could see all the shit in the altsection re-made from banks authority(pos, ico, iipo ecc...)