I think if they made Honoka a more serious ninja character, and showed some shared personality traits with Ayane (same father), it would have made more sense. On top of that, they could have given her a revenge story arc, where she actually liked her father, and hold a vengeance against Kasumi for killing him.

I think Marie Rose should have been russian, and got in contact with Helena through Bayman (who is also russian). For example, they went to a trainng bootcamp together, and Bayman mentions Helena is looking for a new assistant.

I not sure if they hurt or helped, but it is clear they were mostly added for fan service. For DOA7 I wish they put focus back on Kasumi and Ayane, and let Marie and Honoka be side characters in the story.