In theory it is possible but I don't know how to do it with existing functionality.
I would know a solution in Windows. That doesn't help though.
I also would like a keyboard layout independent shortcut behavior. But I guess people got used to it the way it is and now nobody dares change it.
For your problem there is a solution though.
You use the wrong short cuts.
Switching between Windows is alt+tab. Which is the same German or US.
I personally switched to not using either the German or US keyboard layout.
I made my own mix of both.
https://www.dropbox.com/sh/gh1kd018o5edfox/7kO6MfJmnS/keyboard layout
I positively hate the German layout for programming yet I still am too used to it. The switching is also annoying so I simple combine the familiar parts of the German with the good parts of the English (mostly punctuation).
Download the App Ukelele and adjust it to your needs. This more a generally useful thing I found. It won't fix your short cut issues.
ö,ä,ü are moved to be accessible via alt. That is amazingly easy to deal with, they aren't all that frequent and it frees up space for all those nice Slashes.
Especially /,\,[,] are awful on the German layout and so easy in the Engl.
