According Phase one support, XF back dial only support IQ3 ISO control, but I see the dial of IQ180 can make ISO on the XF LCD highlight, change its vale can be easily done via firmware update. Hope Phase one can fix this in the next update. Otherwise, open that software that I can do it for your guys. That is very basic embedded software concept, since the ISO vale on the LCD is contacted. just modify the value via dial moving.
I knew XF controls aperture and shutter speed, but IQ180 controls ISO, as long as IQ180 can communicate with XF with the existed interface ( that is hard to change), to show ISO at XF, that means IQ180 and XF can exchange ISO message. So encode (reuse) other interface command to update both IQ180 and XF firmware should solve the issue.