"The Pope can lead a worship service for Lutherans..."  How did you change the nature of the planned event?  Evidently you have a lot of strings you can pull.  Reports on this celebration has Pope Francis listed as a guest, or if you wish, a co-celebrant - of an ecumenical prayer service.  Yeah - sort of like what Pope Benedict XVI did with Muslims, and St. John Paul II did with Jews....should I go on?  You make it out to be a Eucharistic liturgy, which of course it is not.  Let's stick to the facts and the appropriate words, as I am sure you do not want to sow confusion and falsehoods, do you?