Consider a new coin called USD (or perhaps Digital Dollars or Electronic Dollars DDR or EDR). Perhaps a 2nd new coin called Physical Dollars (PDR or PDL). Some thought might be given to Pennies, Dimes, Nickels, Quarters, etc.
What does THAT do for you? On a 1 to 1 basis, you could track every single dollar created by the Fed. Each digital dollar would be identifiable and unique. An end to digital counterfeiting aka a bank or other entity creating an accounting entry that misrepresents the number of dollars in existence.
It does nothing for me. What it does for the U.S. government is it allows them to track every dollar.
In order to allow fractions of a dollar, you would need to track every penny. I don't know what kind of effort it would take to track 400,000,000,000,000 electronic pennies, but it probably wouldn't be easy or cheap.