What exactly is Kubo plotting by having Orihime remain with Ichigo?

Let's be completely analytical about this. Orihime will be of absolutely no use to Ichigo in the upcoming battle against Yhwach; Kubo has expended Orihime's true purpose back when she was taken to Hueco Mundo. Despite being a likable character, exactly what purpose will she serve during Ichigo's battle? In fact, Orihime being useful further on seems even less plausible as we take into consideration the importance of future battles; Orihime is completely irrelevant to a plot-progressing match against Yhwach. The girl is utterly useless in this situation. So why do you believe Orihime is advancing along with Ichigo in order to battle Yhwach? Offer your opinions below.