If you're familiar with the term, "senshi", then you've probably familiarized yourself with Sailor Moon. Now in all continuities, there are about forty senshi, but we're just going to focus on the Solar System Senshi for now. So, who would be whom and why would you think that? (Note: Emilie-Claire Barlow, who provides the voice for TD's own Courtney, provided the voice of not one, but two of the main characters: Rei Hino, AKA Sailor Mars, and Minako Aino, AKA Sailor Venus, so if you decide Courtney as either Mars or Venus simply because of voice actor, you can do that). Here's what I would personally go with:
Lindsay as Usagi/Serena Tsukino, AKA Sailor Moon: Both are ditzy and super optimisitc, and both have a, for the most part, inseperable best friend (Beth and Naru/Molly respectively) until we start seeing the friend less and less often...
Heather as Ami/Amy Mizuno, AKA Sailor Mercury: Both take pride in their intellect, though one is clearly more stuck-up than the other, not to mention that Ami was mistaken as a monster during her first appearance and Heather, for the most part, is one.
Courtney as Rei/Raye Hino, AKA Sailor Mars: Not just because they share a voice actor, but both are very hot-headed, have music as a hobby, and are invovled in politics (or somewhat in Rei's case; her father is a politician in the manga and live action series), and both have a love-hate relationship with some guy (at least Rei does in the original anime).
Gwen as Makoto/Lita Kino, AKA Sailor Jupiter: Both are pretty much troublemaking loners, but both mean well and can show a bit of their feminine side when comfortable enough.
Bridgette as Minako/Mina Aino, AKA Sailor Venus: Athletic, albiet klutzy, but definitely among the most mature of the cast.