A private currency still provides added privacy guarentees even assuming the steps you've outlined. Private payments would also be useful in a number of countri

A private currency still provides added privacy guarentees even assuming the steps you've outlined. Private payments would also be useful in a number of countries outside of the West. Currency volatility is obviously unsolved but remains an area of active research - Algorithmic stablecoins like Dai and MakerDAO are obvious candidates but live on the public Ethereum blockchain. Private smart contacts chains like SCRT exists but are mostly under explored. Most privacy cryptocurrencies also have secondary OTC, P2P or will have atomic swaps. This is all to say that a privacy preserving stable cryptocurrency is possible.