I agree with what @Mark_Segal wrote above, investing in medium format cameras just for scanning might probably be out of proportions.
One thing though: Depending on what you scan, the wasted number of pixels can differ quite a lot. Most of my (old) analog material is in 645 format with an aspect ratio of 4:3. Here, a GFX would increase the number of usable pixels considerably. Scanning 135 format is best done with a 3:2 proportioned sensor. I’ve commented this in several threads, one of them is this in post: Do I need to change my lens/camera to scan medium format? - #8 by Digitizer
Paper prints have a range of about 7 bits, whether you start with 14 or 16 bits seems negligible - unless you do really crazy things or have to handle heavily underexposed material.
All in all (and apart from the aspect ratio considerations) we’re in that part of 80:20 where cost/benefit is not budget friendly.