New tax engine - Need to be able to set Exchange rate type for sales tax per Tax Registration ID

There's a new feature Exchange rate type for sales tax.

It's a significant progress and I'm now able to set a different exchange rate for tax purposes per legal entity. However, it won't work for our Belgian company that has multiple tax registrations in countries like Poland, where it's required to use the exchange rate of the central bank of Poland (NBP) for tax purposes.