I started this with the intention to not bring transactions into it. Purely from a basketball in-game mentality/coaching kind of discussion.
What would you do, with no trade or FA ability, with the roster as is to help these two play better together?
If they can't be traded, I would keep CJ and Casspi glued to the bench. I think that would help balance both KI and DW mindsets, where they don't feel they're losing shots to an inferior player (more pointedly at CJ). Not that most of the roster doesn't share that same trait, but CJ/Casspi seem to be the most "confident" and willing to jack up whatever and whenever. Seems to take much of any type of flow the offense has completely out. Gee borders that fine line, but he (barely) survives due to his defense and lack of alternative options.
I'd change some of the rotations as well:
Start: Irving, Waiters, Gee, Thompson, Zeller
1Q, 6min: Irving, Livingston, Gee, Speights, Thompson
2Q start: Waiters, Livingston, Ellington, Walton, Speights
2Q, 6min: Irving, Waiters, Ellington, Thompson, Zeller
Kind of generic (like not accounting for game situations and it's not meant as a minute by minute sub pattern), and I'm sure the metric-nazi's can look deeper. But some sort of rotation like that could give each KI and DW some time together, as well as some time apart, for them to do some work.