I know half a stop isn't all that much in a lens with 3 effective stops of stabilization, but I primarily use my telephoto for stage performances, that can be fairly dimly lit. and still needs a reasonable shutter speed like 1/100 despite the OIS. I know I should be looking at the 50-140 f2.8 instead, but it's a much too expensive lens for me. If I could afford that, I'm better off replacing my Nikon 80-200 f2.8 AF-D with the 70-200 f2.8 VR II instead.
Thought 1) If you have Nikon 80-200/2.8 (any version) and it works for you, why switch to the Fuji 50-140 anyway? As you've observed, it's a very expensive lens - beyond my reach too. And far bigger than I prefer.
Thought 2) Have you considered a very fast, high grade, adapted prime at the FL that you use most frequently? I'm thinking 100/2, 105/1.8, 135/2, 180/2.5, etc. You could also add a TC or speed-booster to vary the FL in suitable situations. Eg, with a 100/2, that would give you a 70/1.4 - 100/2 - 140/2.8. Just an idea.
Cheers, Rod