I believe it would be a great improvement to be able to export data (invoices especially) to UBL.
UBL is an international ISO Standard and has been approved by the European Commision (article1). Being able to export to a UBL-xml would enable accountants al over europe to import the data into their software.
Indeed, the UBL Invoice is the only XML Invoice document standard that is sanctioned, stable, integrated within a suite of supply chain documents and is the nearest thing the world has to a purpose-built ebXML document format.
4 Part article on UBL (very interesting!): UBL is an ISO international standard, so now what?
The UBL 2.1 Standard by Oasis: UBL 2.1 Docs
Invoice structure + example in UBL 2.1: UBL 2.1 Docs - Invoice
I’m aware there are a multitude of xml schemas being used though (UBL 2.1, Finvoice, OIO, Svefaktura, ZUGFeRD).
I suggest a XML-exporter with schema selector.