I've never had a client ask for UHD or 4K footage, but it's a handy format to work with in post. Being able to re-frame a shot, simulate a pan, simulate a slow zoom, down-res to 1080 4:4:4 color, are useful options to have when editing.
Some of the large distribution channels specify 4K delivery ( Amazon-Prime, Discovery Channel, Netflix, Yahoo, etc... ) in their contracts, but most of us won't be shooting for these companies.
The camera would record no audio at all when shooting at 125 fps...
Page 43 from the US Sony FS7 Manual
"Audio recording is not supported in Slow & Quick Motion mode."
All of the cameras that SkyCam manufacturers that are used to cover the Super Bowl and other sporting events all use CMOS sensors, but they shoot in global shutter mode : http://www.skycam.tv
There's an interesting color grading YouTube channel ( Aram K ) that has a video that covers how to buy a lower cost computer monitor for color grading.
Definitely worth checking out : https://www.youtube.com/watch?v=nqwHTEjjhzA&t=3m13s
For editors using Vegas Pro there is a free Vegas Notepad extension from VASST Software : http://vasstsoftware.com/freeware/
It's the last download link on the VASST web-page. This Notepad app can store your notes right inside Vegas Pro project files ( .VEG files ) or to an external text file if you set it up that way.
LUMIX GH5 High ISO Grading Test ( up to 10,000 ISO )https://vimeo.com/201425168