For me, the hybrid view finder on the X-Pro is a neat feature but not really that useful at long focal lengths. I typically look through the viewfinder with both eyes open and only close the left eye to concentrate on reading the information from the electronic portion. When tracking targets, i have both eyes open so it is nice to see the close-up view in the right eye using just the EVF rather than a small box representing lens field of view. Maybe this sounds weird and I am missing something an OVF would provide.
Anyway, there are a few opportunities to trim cost on a notional X-E3 based off the X-Pro2:
Hybrid VF -> EVF
Remove ISO from the shutter speed dial to lower the dial's complexity
Remove joystick (as much as I like the concept), perhaps one or two of the programmable or more remote buttons attached inside by long flexes, then transfer some of the functions to software
If enough money is saved maybe a touch tilt screen can be added. (A tilt screen is more easily damaged than a fixed one, adds a lot of mechanical complexity, and divides the camera body into two, sealed pieces, some structure, and a sealed electrical cable between. It is very useful but not without significant cost and reliability impacts, which Fujifilm would transfer to the customers.) An OLED display with an integrated touch sensor costs more than a LCD but is visible over a much wider field of view. Hopefully, it can be dimmed more than the LCD, too. (As another side note, the front of the camera and the image sensor should measure subject luminance levels and adjust both the OVF and rear display luminance to better match. It is inconvenient for me to be blinded by the camera in dim environments.)