It's the "hopefully always up-to-date" that is my concern. There are, at minimum, 28 different rates to monitor here. They can be changed arbitrarily by their

It's the "hopefully always up-to-date" that is my concern. There are, at minimum, 28 different rates to monitor here. They can be changed arbitrarily by their national governments, and in at least one case already such a change has been made with just a week's notice. Even if you're only checking those rates against your existing look-up table manually, the effort to do so at least every week is going to add up. There should have been an authoritative, machine-readable source for this data from day one, and vendors should have been able to rely on that data and protected from consequences if the authorities provided incorrect information and vendors acted on the incorrect information in good faith.