Grug
Veteran
The problem with the Z-Finder is that it prevents the LCD from being used for touch-tracking AF, which works amazingly well on the FX6.
You can flip the Zfinder up to activate tracking obviously, but certainly if you had your eye to the loupe and wanted to tap mid-shot. That's going to be a problem.
That said, it's probably almost as difficult to do with your eye pressed to a dedicated EVF and the LCD mounted separately for tapping on.
I feel like using the stock control handle that comes with the camera (and using the joystick on that to shift the focus point) is probably the best compromise to that (if you're shooting solo).