The existing solutions are not optimal, IMHO. I'm still waiting for something better to come along. There is a possible solution, but it would take some fabrication to build it. Kawasaki could, of course.
Notice how the 2015 Versys 1000 top case is attached. Notice the grab handles on the Versys that mount the OEM saddlebags -- the same bags as those on the N1K -- have attachment points drilled into the ends for an OEM rack. That could be done to the custom grab rails that come with the OEM saddlebags and replace the original grab handles. They are a different design, but by drilling and tapping two holes on each side in their ends someone with skills could fabricate an adaptor. With those mounting points (and maybe a secondary support on each side), a rack could be put in place to hold a top case. Maybe even the Kawasaki case, or at least a GIVI plate and case. I half-way thought maybe Kawasaki would do that for the 2016 N1K and it would retrofit to the 2014 and 2015 models.
Still waiting.