OpenText VIM: How to implement a custom filter to delete certain E-Mail attachments?

Question

For incoming invoices (via email) we want to delete all attachments which are unequal .pdf. The class and method which are responsible for this are:

/OTX/PF01_CL_REGISTER_MAIL

• /OTX/PF01_IF_REGISTRATION~REGISTER
• GET_ATTACHMENT

At the moment I consider to solve this via an implicit enhancement spot in the method GET_ATTACHMENT.

Would this be the best solution or does the VIM module have any Business Rules, Customizing, BAdIs, etc. instead which would be more suitable for this kind of 'enhancement'? If yes can someone provide more insights?

System is running on S/4HANA2020 On-premise.