Not only did Skye have superpowers, she also had the potential to become a top network specialist.
She could fight and offer support; more importantly, she was a 20-year-old girl.
It was very easy for a woman to keep a secret, and there was plenty of room for her to grow.
Luke had already been training her for the past two years.
Speaking of which, Skye could be considered the "student" whom he had put the most effort in.
Mindy was good, but she didn't have superpowers.
Carol was good as a personal bodyguard, but didn't have enough smarts.
The twins were already making him money, but was he someone who lacked money?
Lorna had given him even less; now that she was pregnant, she was out of the game.
As for Stacy… Luke couldn't dwell on her without feeling stifled.
After all these considerations, Skye was the only one who had the right mindset, and who could think and fight.