As I understand it the FujiFilm camera remote app does the same thing you like about the X1D, basically just reads the image off the camera and puts a thumbnail that can be enlarged on the smartphone or ipad. Just like the X-T2 or any X camera does.
This allows you to check the files, zoom etc, and use various iPad software tools on them.
As for tethering via wifi, I don't ever see that working well with a raw file period, just too large a file and too many risks of corruptions during load. I agree needing a router is a problem.
Best solution for tethering is the way C1/P1 do it, at least for me, but odds are that will not happen for the GFX or any other Fuji camera.
Paul Caldwell