Paul Seaton directed my attention to this clear and deep analysis of the pope’s new strategy for engaging Islam by John F. Cullinan. Is it possible to make progress based on shared religious values in the absences of a shared understanding of the truth about God? Is it possibile to agree that any shared claim for religious freedom is based on reciprocity? The value or principle that welcomes the building of mosques in Rome would do the same for churches in Mecca. There’s lot more. Here’s my first use of mugs: 
There will never be a church in Mecca. On the other hand Kuwait agreed to replace children jockeys with robots when it comes to camel racing... and Dubai is interested in a Catholic Church provided it is twice the size of the Vatican and the church agrees to move a lot of nice art and relics to the UAE.
I think being "people of the book"/descendents of Abraham gives some ground for rapprochement...Islam has traditions in that regard that can be used to fight more radical sentiments. Nonetheless, Muslims are taught that theirs is the last revelation of God, and all others are penultimate. In the end, I suspect it will require a long period of good ol’ ass-kicking to take the wind from their sails.
It doesn’t matter much if, in principle, churches are allowed in Mecca. There are no Christians in Mecca, and none or virtually none living (as opposed to staying) in Saudi Arabia. Christians are not moving into the Middle East, so there is no market for new Christian churches. Muslims are moving into Europe. Encouraging mosques in Rome is not equivalent to theoretically allowing churches in Mecca, which the Saudis would never agree to anyway. The urgent task right now, it seems to me as a non-theologian, is to rebuild the West’s sense of itself as a civilization. An important part of this is to behave more confidently and defend ourselves more decisively in an immediate political sense. If we want dialogue with Islam, it will be much better, much more genuine, and much more useful from the West’s standpoint and probably from the standpoint of reasonable Muslims, if we get our own house in order first. And our house is not in order.
Great article, and encouraging. Hopefully there are Muslims out there who actually realize what the Vatican is doing and feel obligated to respond, but I won’t hold my breath. It’s really amazing that when the Pope implied that only barbaric peoples wage holy war and that Christiandom has abandoned the process that the dar al-Islam responded by calling him a crusader and shooting a nun in the back.
Once again, thank you (and Paul) for following this and posting.