If you need the exchange rate to be fixed for the additional reporting currency for any late additions after the asset has started being depreciated you have to amend the exchange rate manually which is prone to error and could lead to a balance being left on the additional reporting currency at the end of the assets life.

It would be beneficial for Business Central to calculate what the new exchange rate should be based on the amount of depreciation left in both currencies and automatically update the rate on the depreciation book.