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.
What if people with kekkei Genkai have an equilibrium of yin and yang in their body(like a little where they combine the elements to produce the Kekkei Genkai) which in turn lets them combine their respective elements to create their kekkei genkai elements.
Now, this is what an awesome chapter looks like. Unlike the previous chapter, it had wholesome moments and funny parts, and the title was done justice at the end.