Devil_Hex
It is enough for the MC to make them strong at Jonin level. They will never be fully loyal to the MC. The MC cannot seal them because of their positions. When the MC learns about their Kekkai genkai, they become worthless for his precious time.
Let's assume that he made them strong at the kage level. But they were affected by the will of fire and other ways of thinking. When MC becomes enemies with Konaha in the future, they can attack him. Or they will be people who change the course of events independent of MC, in the future plot. Since MC cannot fully manage them, their powers will become MC's in the future. It may cause difficulties. Why not?
DaoistVZOzSm:(Google translation) Friend, where in the story does it say that they are going to betray him when he makes them very strong? Why do I think I missed it?