Well using those tables for reports is generally a bad idea, primary because you can delete them after you have printed the invoice reports.
So I think, if it was me, then I would be looking into adding the FCY fields to the VAT Entry table. But of course I needed all the details in regards to what the purpose of the report was, to know why it is so important to know the VAT in different currencies, as VAT normally ALWAYS is in your local currency when reported.