I take your point, a well designed centralized system by a competent, benevolent government would be better than having to rely exclusively on a set of private banks not beholden to a constitution. My concern there, given the track record of most governments, this will not be built without tools for control, even if they are not used right away.
It also sets a precedent for government involvement in individual transactions. Today we'll have an optional cashless payment system, tomorrow banks will start shifting over to keeping accounts with the government directly, the next all financial services will be required to use the government system for transaction processing to simplify monitoring. Anything to stop money laundering for terrorism, you know.