I have been looing into this topic as well and have thought of something:
Maybe consider packages to have option for setting aditional currency but in the same package.
When in the url the currency is set it shows currency, this method has no currency convertion.
Its just an idea we believe it to be a simple approach, fixed prices for each currency in package.
Reason for this idea is to avoid having to create duplicate packages and to have to hide duplicate packages in main order form.
Also if client wants to add more services i would only show active packages "main currency" it it all becomes a mess.
Curreny exchange would work as well as long as no duplicate packages would have to be created, i like fixed prices.