how to enhance FI data source

hi experts,

        I am wondering about enhancement for financial transaction key figures (such as 0FI_GL_06) and line item (such as 0FI_GL_04),  it can be implemented by following:

        1. adding enhanced fields into customer includes.

        2. compile FM for populating date into enhanced fields, and write this FM into table TPS31

        3. adding enhanced fields into extraction structure.

but can I implement this enhancement by standard process by RSA6 as follows ?

        1. in RSA6, enhance extraction structure

        2. populating enhanced data by user exit RSAP00001.

Many Thanks,