A reserve currency is a foreign currency held by governments and central banks as part of their foreign exchange reserves, used for international transactions and investments.
Now tell me that central banks are not the most essential part of the fiat system. Tryvto think outside the box. Without central banks, no fiat and also no need to have gold, USD or Bitcoin reserves.
You fiat NGU guys are tied to the fiat system. It's hard for you to imagine anything beyond it.