Mark only few contacts from a batch in CX App as completed
we have a CX App for Responsys Program where processing one contact can either be instant, take several minutes or even hours. The application creates a request for phone call in a Call Center System and waits till it gets the phone call result code. Till now, the customer was using the app in real-time programs and we processed only 1 contact in each service invocation. But the customer want's to use the application in programs running in batch mode (started by Connect Event or Get Audience) - so we may now receive multiple contacts as part of a single invocation.
Looking at the API for Product Import Callback and Completion Callback, it seems to me, that when the CX App is invoked with a batch of multiple contacts, it can set ETVs individually and repeatedly, but the Completion callback (or release flag in Product Import Callback) can only be called once for the whole batch of contacts. So all the contacts must wait before the last one is processed.
Is there a way how to divide the batch in a CX App or mark only selected contacts as completed and let them advance to the next stage of the program as soon as possible, but allow other contacts from the original batch to wait before their processing is finished. I expect negative response, but maybe I'm missing something.