Sage 200 Fixed Assets Module - update coding can be changed after depreciation

If an asset is reassigned to a different dept/service, the depreciation charge to the P&L cannot be updated once the asset has been depreciated for the first time. This results inaccurate depreciation charges to the P&L. Currently the asset needs to be disposed of, deleted and the charge on disposal (which isn't a true cost) being journaled to correct this, and the asset then being created again. Or setting up a recurring journal between the P&L accounts - either way more long winded than what it has to be. What is the reasoning behind not being able to change the P&L coding?