Hi Rahul,
In one of the implementation on HANA we did for a Hitech Major in US, we implemented the custom security using User table and Role table.
That client has his own internal user id which is used for SSO purposes. So based on that user id and with help of those 2 tables we were able to implement security using "function" and re-using the function in the Reporting "procedure" .
We didnt use AP to do the authorization, instead we wrote our custom Function to do the same.
It was implemented successfully and went golive ( already 3 months finished).
Regards,
Krishna Tangudu