Regarding the first argument (apps with multiple panels), the author should try Linux. Gimp (and others) works fine on Linux with sloppy focus. The global menu

Regarding the first argument (apps with multiple panels), the author should try Linux. Gimp (and others) works fine on Linux with sloppy focus. The global menu bar is indeed a problem, but it can be alleviated by adding a small delay before changing focus (so fast mouse movements to reach the menu won't change focus).