You cannot have a single sovereign country without a central sovereign currency. This is a recipe for the breakup of Argentina.
Argentinian provinces have issued their own "quasi-currencies", both in 1985 and early 2000s (link). Issuing alternative currencies during a inflationary cycle, without security other than the hoping to force the central government into eventually buying it out, only perpetuates the problems the currencies were created to address.
Milei rejected alternative currencies or buying them out the week before Armstrong wrote this. Not only will what Armstrong (claims) he recommended will not work, he is pretending after the fact he was a key player he never was. He never advised Milei or the Argentinian government at all.