Fluttershy as Heavy (Heavy has "Beware the nice ones" tendencies when off duty)
Spike as the Civilian (the useless tenth class from the previous games in the series. He was the escortee in the escort mission mode. He was the first case of both escortee & escorters being player characters. The escorters were Soldier, Heavies, & Medics. The ones trying to kill the Escortee were Snipers. Sniper's camper bobble head is The Civilian. This has to do with Spike because he tends to be useless in combat)
Redheart: Medic (I imagine she's a little unhinged from the kinds of crap she has to deal with)
Zecora: Sniper (they both have a wilderness aspect in their backgrounds)
This actually makes sense, in a way. I hope more will do that. As it stands, I'm glad you did, because your art is awesome. That shading and texturing here is top-notch, from the hair to the launcher. And the lines, 'course, they're darn near perfect. Well done!
To all the people saying "Isn't Twilight the Sniper?" I say "Yes, but it's always nice to play a different class for a change. Pinkie Pie could make a great Heavy, for example (especially since she actually used Twilight as a magic-minigun during the Changeling Invasion)."