i think you ve read too many da vinci codes and conspiracy theories
i doubt Gantz, or Hiroya Oku has an underlying religious message, if he did, i think he would have revealed it by now. Take Evangelion for example, they were fighting "angels" from day one, they werent giving any room for subliminality, not even in the ending, blunt, cold-served drilled-into-your-brain psychology.
the fact that there is a cult behind Gantz in Germany doesnt precisely give it any heavenly status. If everything thats created a cult could be called heavently then we may begin ending our prayers at church by "in the name of the Gatts, the Griffith, and the Holy Pakk, BERSERK"
the Deutsch Ball may just be an alien artifact, and like anything that causes fear, creates commotion and fanatics.
and by the way, i believe Deus ex Machina is usually referred to when an author recurs to gods or another omnipotent entity to fix an otherwise un-fixable conflict in his story