Having Jonathan Kuminga sign his $7.9 million qualifying offer would be an unmitigated disaster for the Golden State Warriors, but they would be able to salvage something in the form of using the Kyle Anderson $8.8 million trade exception.
Given how close the Warriors would be to the first tax apron even with Kuminga signing the qualifying offer, the Warriors wouldn't necessarily have the capacity to use the entire trade exception. However, they may be able to fit in a player making less than $6 million or so, with one obvious name already a candidate to be acquired in such a scenario.