I fail to see why the HTS would not work. Support in focus is trivial, the work is already done for the H5D-50c which uses the same sensor as the X1D. The HTS is a selling point for the H camera, so there is a commercial incentive. The mount adapter must be sturdy enough to hold the HC 200, HC 120 or even the HC 300 lenses, the HTS is comparatively light.
As to tethering, Phocus should support the X1D on an USB connection. I think I have read that the present demo models present themselves as H6D-50c so as not to upset Phocus and that tethering has been demonstrated. I would expect the production models to use their real I.D., of course.