Yes it is interesting. However, Michael E has shared his observations on the Hasselblad vs D810 and with upcoming D850 I think this will be a difficult time for Hassy. 300ms is a long time.
I've had an opportunity to work with both the X1D and the GFX and they, indeed, were fascinating. Personally, I like the X1D's color... a lot. Now that it may have an standard-type shutter, that is good news. Still, The D850, if it checks out like it's features claim, will be a better bet for me. Trying to mix and match lenses from other systems, non-native lenses, sounds like a plan, but IMO, in experience, they never quite measure up to quality lenses (if they exist) for the system-brand you are using. Non-native lenses smack of jury-rigging and, ultimately, I find myself wishing for native lenses that are well corrected, fast, and sharp. If the X1D could take F-mount lenses happily and they worked out a lot of fine points that I don't find on the X1D, I would be interested. But, both the X1D and GFX, by the time you outfit them with batteries, their lenses, and everything... just are not worth the price to me. Just my two cents. The D850, if it is good, is Soooo much cheaper... and for my work...probably as good or better.