Multiple Backends, e-Sourcing

Hi all, we have positioned e-Sourcing at a client that now intends to integrate to multiple backends. With the SAP Consulting Note (OSS), we can interface e-Sourcing to a single backend. Does anyone have any experience with integrating to multiple backends? Some of our initial white board sessions to resolve this include:

1. Writing some code/scripts or mapping with PI/XI to mimic the SRM BADI "determine logical system" to route the contract back to the appropriate R3.

2. Using the Portal function "Composite Application Framework" to facilitate the selection of appropriate backend systems.

If anyone has experience or comments, please provide details or point me to some documentation to support this effort. I assume someone has addressed this previously. thank you.

regards,

gary