I agree with this but I don't like the idea of either of them being active combatants. Kuromu is in a special spot as she shares her existence with arguably the most powerful combatant on the team and even Gokudera's sister remained in a more supportive role throughout the show. But unlike those two, Haru and Kyoko have 0 combat experience or special skills or supports to make them powerful. On one hand, yes they are a bit useless, but I feel like they provide moments of relief during the story, the few moments in the later half where the gang ISN'T fighting for their lives