This 'solves' the problem of dilution, but it does not address the issue of following the flow of tainted crypto-cash, because the root cause of that problem is

This 'solves' the problem of dilution, but it does not address the issue of following the flow of tainted crypto-cash, because the root cause of that problem is that bitcoin do not have identities (they are bosons, not fermions?) This 'solution' is just one of several similar possible schemes that arbitrarily assign a provenance to each atomic unit of the currency, and is not fundamentally more sound than any other. Any scheme like this is pointless without a mechanism to sanction the use of 'bad' bitcoin, and belongs in the realm of cryptocurrency regulation, not blockchain mechanics. A scheme something like this does exist for banknotes, in that if you are found to have a counterfeit bill, it will be confiscated. The only reason this does not have a stifling effect on the use of paper money is that the probability of this happening to you is slight.