I think the "Equestria Girls as Sailor Guardians" idea is a great one, much like the "Disney princesses/heroines as Sailor Guardians" theme. Unfortunately the MLP:EG version doesn't seem to have a lot of good fan art out there. There IS some, but not a lot; the best I've seen is by YoukaiYume here < Sailor Twilight Sparkle > (follow other links on that page to see the rest).