Thanks for your reply. It seems that the X-Pro 3, X-T4 and X-E4 all now offer the same multiple exposure feature. Just waiting for this to be added to the X-100V and also for RAW final output.
According to the manual the X-100V just has double exposure with basic blending modes although apparently internal processing is the same as X- PRO3. Looking at the firmware updates the expanded multiple exposure feature hasn't been added, not sure why?
If you go to the trouble of producing a multiple exposure in the field then surely you're going to want to edit a RAW version of this file without any additional steps. This is what I would like anyway. Kind regards to all!