"Copy this BAPI and make changes to the copy" is not a requirement. It is a possible way of meeting a requirement.
Copying BAPIs (and indeed any SAP objects) is a profoundly bad idea. It is probably the worst way of meeting a requirement. Making direct changes to the object is to be preferred. For the hard of thinking these are some of the reasons why making a copy is a bad idea
1) Any changes made by your copy to data in the database is effectively the same as making direct changes. You've instantly lost support from SAP if it goes wrong.
2) You won't get any fixes from SAP for the copy.
3) If the original changes between releases, you may find the copy stops working, and you have to re-clone
4) You don't get any notification of the original changing.
So, going back to you requirement. What is it you are actually trying to achieve? What is the FUNCTIONAL requirement.