I've written about this before, but reminder:
A fully private CBDC is the ideal solution, and the only way to replicate the self-custody & anonymity of physical cash
You eliminate multiple unnecessary middlemen - stablecoin issuers, their banking partners, blockchain infrastructure and their node operators, at each step they add to your cost, but more importantly, they control your funds
Instead of Fed > Tether > Ethereum > Arbitrum > User, you go directly Fed > User
Of course, you need strict global consensus for products like LUSD or USDS, but over a decade the market has decisively spoken - USDT & USDC are the dominant types of stablecoin used
The privacy is critical. It can be granular using ZK proofs, so almost all transactions are fully private, and only certain ones marked automatically per legal parameters can be traced. USDT et all offer zero privacy.
I don't expect a major government savvy enough to pull this off any time soon, but I do know this is the right solution to the stated problem