There is not and will not be a central system. The CCP isn't going to abandon their currency for the US CBDC and vice versa. So building on top of an incumbent

There is not and will not be a central system. The CCP isn't going to abandon their currency for the US CBDC and vice versa. So building on top of an incumbent blockchain such as Ethereum would be more interoperable than the proprietary centralized USG CBDC. Though, having seen what has happened with chat, it isn't obvious that interoperability wins in the end versus a handful of walled gardens each hoping to prevail over all others.