Did you miss everything I just said? lol. The current effectiveness of Lauri with or without Kessler does not matter. Building a team around Lauri is not the same as developing Lauri. The best thing for Lauri's development is to continue to play with a variety of different units. Playing a few minutes with a traditional 5 like Kessler is helping his development, not hurting it.
The ironic thing is that this sample size is so tiny, but if you used it you would know that Lauri individually has played significantly better with Kessler on the floor than without him. So if you just looked at what's happened on the court this year, you would come to the conclusion that Kessler on the court with Lauri is a must. Pts, reb, assist, and efficiency are massively up when he's shared the floor with Kessler. It is not close.