Hi Thomas,
Ok, if you are using a Classic Scenario without using SOA,Plase you try to do this:
In ECC:
-Create a Z MF copy of BBP_PO_INBOUND in ECC, modify this to change the call of BAPI_PO_CREATE1 and pass MEMORY_COMPLETE = 'X' and MEMORY_UNCOMPLETE = 'X'
In SRM
-Create a Z MF copy of MF B46B_DPO_TRANSFER. If you have set ERP_4.0. Change the call of the BBP_PO_INBOUND and replace for your new Z MF.
-Set the entry en BBP_FUNCTION_MAP acording the new MF.
-You must to adapt the logic of error handling, because in standard funcionality if the system found any error then it suspend the commit
For service procurement classic you can use active LOG_MM_CI_3 BF and set status in SRM
I understand that you dont use a Extended Classic Scenario because in this scenario you have a "hold" funcionality.
Hope this help you.
Best Regards.
Emanuel