Option 1: Scootaloo and Sweetie Belle. Yeah, I'm already doing my Menoths in the SB color scheme, but this would let me put all three Cutie Mark Crusaders on the same team.
Option 2: A different pony pair, like Lyra and Bon-Bon, Derpy and Carrot Top, etc.
Option 3: Some non-pony set of twins, like Tomax/Xamot or Sideswipe/Sunstreaker.
Option 4: A "straight" Cygnar color scheme. (snort) Yeah, like that's gonna happen.
I've also decided that my Stormcloud will be done up as my recurring superhero design Paladin (who has Cygnar-ish colors already, but with different weighting and shades), and when I feel up to making the modular Heavy Warjack sets (Avenger/Centurion/Hammersmith) they'll be Iron Man and War Machine because of the modularity and the layered geek references.