Very interesting. Was not aware of this. "Chancellor" of Germany isn't very happy about it obviously. I think the EU was good in the sense it increased cooperation between participating states and we see this in the incredible military developments throughout the years. The Euro Fighter and newest Leo 2 developments.
Ironically, The EU is very well prepared to defend itself from outside threats such as a Russian invasion, But just like the US very ill equipped to deal in inside problems such as ISIS sleepers within its borders. Then again no one really is prepared to deal with the ISIS treat efficiently.
I think separating itself from the EU will have negative trade affects on the country. Germany wouldn't want other nations to leave the Union hence it would make an example out of England. Then again it would increase its trade with N.A which could be enough to compensate..