Is there any other way rather than the CATS to integrate with the PS module?
I do not feel there is any other way than using the CATS for HR/PS applications.
This is because of the fact that CATS is built in the SAP_APPL (Check package 'CATS) layer and the configuration customizings lay in the SAP_ABA (check transaction CAC2) layer which is the common platform which all modules can access.
Hence, using the CATS we can achieve the HR/PS integration.
Hope it solves your query.
Thanks & Regards, Swapnil Mishra