It’s a good idea on paper, that’s assuming Europeans want to be “European”, and don’t let in millions who don’t want to be “European”.
I do not want to have a barbarian migration from the Middle East like Mrs. Merkel does. Born into Lutheran national socialism (her Father was a socialist priest in the former GDR), she ignores democracy and formal law. This turned out into a political disaster when it came to illegal migration. She burned her fingers when she invited muslim hordes into Europe. Her CDU broke in parts (the AfD persist completely of former CDU-voters), the EU did not participate and for the first time there is something like opposition in Germany.
Beside of that we need open boarders within Europe. Young people from Greeche or Spain must have the possibility to recived work and education in middle and northern Europe. We even need immigration from everywhere, but only those people that are suitable to us.