You can use a combination of mapping table and applymap.
Example of adjusted script syntax:
LOAD * INLINE
And for your QVD use the following load:
APPLYMAP('MappingTable', FAMILY_ID, FAMILY_ID) AS FAMILY_ID,
The disadvantage of this solution is that your QVD load is no longer optimized (= fast). Maybe you already have a resident load later in the script in which you can incorporate the function?