OK, but the devil is in the details. Can you explain what such a coin would look like? Does it involve mining? Is there a block reward? Is it centralized or decentralized? Is it "backed" by something like dollars or gold? Can you send it internationally? Are transactions reversible? Are transactions/accounts anonymous, pseudonymous, or linked to a real person? Are balances confiscatable? What authority decides? Can that authority inflate the money supply? Does it follow the same AML/KYC procedures as our current system? Are there multiple such systems in each country/region, or is there one main system for the entire world?
Well, there are significant problems with Bitcoin at the moment. Those problems could be alleviated in the future, but in the meantime it leaves the door wide open for a centralized coin.
It would solve the problem of price volatility. Say a big bank issues a cryptocurrency, they'd have a much easier time keeping its initial price stable. Keep in mind that they can toss out the 21million number, or the halving block rewards, on a whim. They could peg it to some commodity, or even a basket of currencies, and get something that's pretty stable right off the bat.
It would also solve the problem of wallets. People have to jump through all sorts of hoops to keep their Bitcoins. This is already a bank. They're already in the business of keeping people's money safe. So it would make sense to have them keep your online wallet. And with that comes things like FDIC insurance. Increased security relative to making an offline wallet.
And it would keep all the benefits of a cryptocurrency. You'd still have instant transactions. You can still send money across the glove in seconds. All that good stuff.
Now personally I think something like that would be horrible. I'd never want to use it. I'd probably stick to cash. But there's no doubt in my mind that if they pull a stunt like this off, they'd get much wider adoption, at a much higher rate, than any of the current cryptocurrencies including Bitcoin.