The question which fiat currency to use could probably be solved by using a composite of the most widely used fiat currencies. In the end I still see 2 challenges:
1) Defining a reliable exchange rate source. So far Bitcoin is pretty much self contained without relying on external information sources. Not even timestamps are fully trusted.
2) This still wouldn't prevent a fee market from emerging. Someone will always be willing to pay a premium to get first in line, regardless of whether you calculate the price in fiat or BTC terms. As a result the fees will still increase according to network load factor.
/thread
1) Defining a reliable exchange rate source. So far Bitcoin is pretty much self contained without relying on external information sources. Not even timestamps are fully trusted.
2) This still wouldn't prevent a fee market from emerging. Someone will always be willing to pay a premium to get first in line, regardless of whether you calculate the price in fiat or BTC terms. As a result the fees will still increase according to network load factor.
It's better to use Bitcoin imho. All Fiat currencies are unstable, and it would be difficult to know which one to choose.
/thread