Would be nice, if we can change the language and currency of any sales quote,
I guess 3 currencies, Your local currency, euro and us dollar would be great.
Also sometimes you can send english quotes instead of your local language, would be nice if we can choose these inside the quote.
You can temporarily change the language under Preferences, but the change is global and cannot be made to apply only to one document. When you change back to your normal language, all documents will change back.
Currencies, however, are associated with customers. So if you want to provide a quote to a customer in multiple currencies, you need to create multiple versions of the customer with different currencies. You can certainly do this, because sales quotes have no financial impact.