Am I gonna need Sunday?

Hi, I skipped Sunday because I don't care for men with long hair but I really want Castorice because purple is my favorite color and Sunday may be the only Harmony unit that can buff the Servants.

Do you think I'd be able to use other Harmony units? I have E6S1 Hanabi and E2S1 Robin. I'd prefer to use one of them if I can but knowing Hoyo, they'll make Sunday mandatory for Remembrance path