Is there already a written confirmation from the immigration office that he meets the requirements for a Beschäftigungsduldung? In such cases, I always apply for a Beschäftigungsduldung at the immigration office and wait if they confirms it can be granted. Prerequisite for a Beschäftigungsduldung is not a passport, he just has to have a "clarified identity". So he could first present a birth certificate or similar and see if that is enough for the immigration office and later the passport.