The fast attack vehicle is a patrol buggy used by the Brickville Union army. They're based on an older Dino Attack Lego set.
It's small size and high mobility are favoured by some commanders. They're valuable for patrol in all kinds of terrain. They are also used as light and fast escort vehicles.
I remember these sets. In fact I had considered doing this idea for conflict, but the costs of these sets if you can find them is unreal. Good job on switching the colors, I always like a good dune buggy.