In order to have the currency conversions one could also use other services, creating an FX watchlist and populating it with data obtained from other sources works as well. This is actually what I do. I am using RE Ed1 and I couldn't see the Oanda FX service in my available services list. Am I missing something?
You are doing it correctly. The free Oanda service is actually only for interest rate data, so you can use it if you want to simulate interest applied to forex positions held "overnight."
More importantly, I appreciate the motivation of providing an easy to use currency plugin but I don't think this really answers my question.
Essentially, I can not really see why would you would like to limit the available currencies for assetts, especially while not providing a full list. (the currencies that I've provided above are all from MSCI world contituents stocks' currencies, so they are not that exotic.)
I think we originally went with an enum to help prevent people from entering an invalid currency, because we wanted to standardize the currency names (in case two different services used different abbreviations for the same currency), and because we thought we would be able to cover all the currencies in the enumeration. I think experience has shown us that it would be better just to use a string. I've added this to the todo list.