Again, it shouldn't be over the top, but it'd be good to find ways to draw from and add twists to the existing tropes and archetypes. They're my least thought out idea so far, but I hope I can make them very interesting.
Either way, they won't come out being the typical Sailor Moon type characters (they might just be girls gifted with powers, and not ones that need to transform and look all silly). What I do know is that they'll be very agile and acrobatic (I love the 'standing on a telephone pole' thing) and focus on more passive abilities (sleep, purification, maybe healing, shielding, and any given guardian won't be able to do it all).
I hope that still holds your interest.