When he decided to give Kate the evolution serum, Michael had already made several preparations. His intentions were clear, he wanted her to obtain more abilities.
While the rapid adaptation ability was incredible, it needed time. By the time that she grew to the full potential of the ability, who knows what could have happened in between.
The best way of ensuring her safety was by making her strong. After all, he could not always be around her. Additionally, while most of the time, she was usually with Lina, who was supposed to ensure her safety, nobody could tell what would happen.
If the attack was not detected on time by Lina, Kate might end up getting hurt before Lina could do anything. Therefore, to avoid something like that from happening, Michael decided to increase Kate's strength.
