Peterh,
I would really suggest taking another look at the X-T1. I know you said you are more into the RF design, but if you're thinking of going A7 ii / A7 R ii then it would be a switch to a mirrorless DSLR just like the X-T1. Only difference is that in my opinion, the X-T1 keeps your fingers on the body and not in the menu's like the A7's do. I have had the X-T1 for over a year now, and there is no other camera out there that lets you create such a tactile relationship with your camera, aside from older 35mm's and range finders. The X-T1 is also leaps and bounds ahead of the Pro 1 in terms of performance, so you might be surprised when you slap that XF 35mm 1.4 on an X-T1 body with an up to date firmware.
I agree with one great tempting feature of the A7's and that is the larger FF sensor. I have a canon 5d3 with similar primes to my fuji X primes, and although the fuji's always make fantastic sharp images, there is always a difference i see in dimension and depth of field between the fuji and canon, and i really think it's something that comes from a larger sensor.
I have never had a sony A7 series camera but the few times i picked them up at the stores to play with, they always felt a little distant from my intuitions, but maybe that's something that changes with time and usage. If you can wait, i am sure there will be an X-Pro 2 and also an X-T2, but it's not really about waiting anymore because once they release a new camera, there is already a successor in the makings these days.
Has anyone tested the firmware 4 with an 18mm f2? I would be interested to see how this firmware improves upon all the launch lenses? Especially since it has turned the 35mm 1.4 AF completely around! Holler, Gavin