All currencies have pluses and minuses. There is no holy grail of a perfect currency.
So the answer is to allow efficient translation between currencies. This requires a standard language to create that efficiency.
It allows the individual to hold all their wealth in any form (eg. gold, land, wheat, rice, USD, Yen, Euro, Bitcoin, etc.), and have it "translated" electronically when conducting a transaction.
I term this "wealth translation".
A Visa card that debits your Bitcoin when you purchase something at the grocery store. The grocery store receives currency of their choice, Visa debits your Bitcoin. A "wealth translator" takes a small fee on the transaction.
See below for the working prototype. An exchange software that works for any transaction (grocery store to central bank).