The Dazzlings: Adagio Dazzle, Aria Blaze, & Sonata Dusk; team up with the Shadow Five: Sour Sweet, Sunny Flare, Indio Zap, Sugarcoat, & Lemon Zest; to counteract with the Rainbooms, plus Starlight Glimmer. We all know the Shadow Five are Crystal Prep counterpart of five of the Rainbooms: Fluttershy, Rarity, Rainbow Dash, Applejack, & Pinkie Pie; while the Dazzlings, being from Equestria, would act as the counterparts of Sunset Shimmer, Starlight Slimmer, & Twilight Sparkle.
The eight don't even have to become villains again. They could probably have come together and star in their very own Equestria Girls spinoff. They can be just like Humane Eight, but with a completely different dynamic. They can even get that dragon OC girlfriend of Spike's, Emziko in dog form.