Kanter is rendering himself unplayable with his defense today. He'll never be a stopper, but we need him to be better than this if he's going to see the court.
You need someone to cover for his defense, I think everybody knows that. Kanter had his best seasons in Oklahoma City and New York, where he always had Ibaka or Adams and Porzingis to bring the necessary help and rim protection.
Playing a system of four guards/wings + Kanter is suicide. That will be lay-up after lay-up, you can't outscore that.
You need a guy to add that interior defense and let Kanter focus on beasting on the boards and scoring in the post, he's one of the best in the league at that. Kanter is a specialist, just like JJ Redick. Players who can bring something extra, but you know you have to be careful with whom you place them on the court.
For the whole season Grant Williams has been his buddy against other bench units and they have done a great job at that. When everybody is healthy I'd like to see either Theis or Robert Williams also get some run with Kanter.