The most likely way I can see this happening is for someone in each country to write a localisation to produce the XML report. For an example of the sort of thing that can readily be done now see
Clearly the specific interface to efficiency use it to export invoices is not in place but the programming interface is appropriate. The produced file could then be sent to an IT interface service provider, as is currently done in several countries localisation using text files.
Lubos was apparently intending to extend the capability of the localisation system. I don’t know was the current plans are.
Why not just uses a custom field if type list