Hello Jay,
I am not answering your query, but sharing with you a useful link to wiki page. This wiki page has a list of Useful BAPIs, User-exits, BADIs, Function Modules etc from APO and also contains link to various child pages on technical side of APO. You may want to refer this if not done already.
APO-Technical - Supply Chain Management (SCM) - SCN Wiki
Other experts can definitely share if they have any input.
Hope this will help.
Thank you
Satish Waghmare