Hi Jim,
There's an additional license cost to install the SAP Integration Package for SWIFT (SIPS) for PI.
So I would recommend that it's not worth paying this unless you are planning on using SWIFTnet for your bank connectivity.
A possible high level approach you could take:
Outbound:
Payment runs --> Approve batches in BCM --> DME/PMW files saved to application server directory --> files picked by PI --> PI Sends to Bank using SFTP
Inbound:
Bank creates Payment Status Report (PSR) files and bank statements --> Places on SFTP server --> PI picks these files --> PI transfers to application server directory --> Upload files into ECC (e.g. program FEB_FILE_HANDLING for bank statements).
I think this would be the simplest and most cost effective method for a single SAP-to-bank interface.
If you use multiple banks, then it would be worth looking into the SWIFTnet option.
Hope this helps,
Jack