We are discussing different provisioning approaches and the interim state during the time the old provisioning system and CUA are gradually phased out.
Is possible to perform direct provisioning with AC10 to a client that is currently a CUA child? Or is the only possibility to connect AC10 to CUA?
I hope you are making the process too complex When you are provisioning the users from GRC CUP, why did you need CUA??
The purpose of CUA is to manage the users centrally. When you have CUP, you will never manage the users directly in which case you will have to use only CUP.
Please refer SAP Note 1099011, which might be handy to understand the complexity and limitations better.