Hi,
my opinion - "Yes" - if they're only used as securities and traded on "money market" in order to hedge your investments or make quick cash. Basically - only US Dollar will be used to buy/build/trade things in-game, and other currencies will be available to invest in and stockpile as investment for the future. Their movement up and down against the Dollar with provide you with either losses or gains in the "money market". These currencies will move according to their respective economy.
Also options:
- possible foreign currencies - Euro, Yen, AusDollar, Swiss Francs, Saudi Riyal, Chinese Yaun, British Pound, Indian Rupee, Ruble, Hong Kong dollars, etc...
- ability to choose which of these to be in your game, if any;
- ability to deposit your stockpile of these currencies in a bank in the correct country (pounds in London, Yens in Tokyo, etc) for profits via interest. Same thing in lending money: to be able to borrow money from a bank in either dollars or their respective currency in their country, if available
- companies with focus "investment" to add bond and money markets to their strategy
- may be: option to buy land in some countries only with their local currency and pay little higher cost in dollars.
- currencies to be treated as an asset in your statement sheet, not automatically calculated in dollars
- to be able to make business with the goverment in their currency
Also: "gold" to be added in the same mechanics as above, with possible added feature - to be able to buy/sell foreign currency against gold, instead of against dollars.
Also also - pls check this
link for more ideas on Foreign exchange