Hi,
If enhancement will suffice your needs then you can ahead and do it.
You can add required field to your data source extract structure and maintain the required logic(T -cde -CMOD) to fill the data for added field. unhide the added field at RSA6 and do the test extraction at ecc RSA3.
once it worked then replicate into bw and activate data source.
later add required info object to connected target and create transformations,do the direct mapping.
Activate transformations and dtp.
Code you can directly maintain at include program - ZXRSAU01.
Thanks