I am also a bit uneasy about the use of North Nigerian money by the EU, not because I care about them - obviously they had no intention of ever spending that on their citizens or infrastructure. In any case the leadership is there with popular support so they all have to pay for the damage in Ukraine.
More because the EU is going so mental about some things like climate change of women's rights that they might end up confiscating money from people who disagree with them ideologically, not just those who are committing illegal drunk invasions.
Of course the BRICS and oil countries could set up their own currencies and asset custody arrangements. They were talking about it for years.
They will never do that in practice - it's too difficult, it takes money and time and it requires the rule of law which is a big no-no to cruel dictators.
I have some Rand because for all its faults RSA is a democracy with a growing population , I quite often trade in Yuan. But the other joke currencies will never be investible.