This is remarkably simple for an idea, but vintage-ish. How about french twists? They are something that are flattering for the ladies with mid to longer hair (if any of your bridesmaids have really long hair, I can help with ideas on how to french twist that much hair, because I've done it). It's also something that might be more amendable for the ladies who aren't so much into victory rolls or other vintage styles as many women see it as "modern."
I really have never met a woman who didn't look good in a french twist.