By default is a DID is send direct to a user then that DID is used as CLIP for that user.
You can create two ARS tables, one for the users with a DID and one for users without a DID.
Tha ARS with DID have a shortoce like this : ?/./Dial/0 the ARS for other users have a shortcode like this : ?/.SCLI/Dial/0
Then create two user rights profiles, one with a shortcode pointing to ARS with the predefined CLIP and one without.
Then assign the users to the appropriate user profile.