Just wanted to share a word of caution from my experience working with PPOME.
I wanted to assign a user to a position (Release code workflow to work for Purchase requisition release strategy). When I tried in Production it did not allow me to save and got message that client is not modifiable.
Therefore I created a transport with new users adding to the positions I wanted and moved it to ECP. I assumed this would assign new users to the position that I am moving via TP and keep the existing user assignments in tact in ECP. Unfortunately, after this TP was moved all the existing user assignments disappeared except the new users (that existed in ECD organization structure).
After I read on SDN blogs I updated TRSP-CORR via OOCR tcode and moved the transport to ECP thinking this will allow me to do changes in ECP. But this did not help either so seems like my last resort is to make a request to open up ECP so I can update the user assignments to the positions directly in ECP.