Very Nice idea, this reminds me of a conversation we had earlier when we met on the boards, and I'm glad that it finally came to fruition with these pictures.
Most of my GI Joes are placed in stairs, so I can see them better. But my Cobra, since I have many of each, I don't care displaying them in action.
I remember also telling you not liking the grey Headhunter bats because I found they didn't go with many of my Cobra forces, but now I see how they can look just as good with the grey vipers and the right amount of troops.
The grey BATs fit pretty well with my other grey army builder. Also, they all have orange and grey...

You now need Blue BATS (It would be cool if they make them!!! ) just so that they can motivate your blue Vipers and prevent them from deserting the battlefield, yep that's what BATS are best known for.
Not sure about the Blue BATs... But maybe a all Black and grey BATs (like the ROC EELs) should look cool! One blue character I would love to have is a Blue Female Trooper (like the 2007 Night Stalkers Shock Troops).

You could get a couple of TRAHC blue Undertows to go with your blue Hydrofoil, they just seem like the natural choice of blue frogmen.
Maybe a good Idea, but I'm not a fan of this character... Maybe if I see one in my hands one day...
Are you intending to have same single characters in all of your factions ( Ex: blue Firefly, red Firefly, grey Firefly )?
Or does each team have their unique commanders and specialists?
I only collect the one I like. So, I don't need a Red Firefly (or its arctic version). In fact, they look strange IMO...
So Storm Shadow leads my Arctic troops... not because he looks like an Arctic trooper, but because he is white (at least for now :shifty:
Martin