Fixed Asset Cost (Future) Constant

We are on 9.0.   On fixed asset constants for the 'Cost' of the asset the application only allows the 'Default', however, for accumulated depreciation, expense and revenue the user can chose either the default or responsible BU.   We would like to track our NBV (cost and AD) via the Responsible BU.  We have looked at the program P001012 and can see no reason why changing the Cost to look at the Responsible BU would cause any issues.   I believe that this constant has always been set to only allow the 'default', but do not know what the 'future' is there