Also, I am trying to remember without having to look this up, but this armor was made up of three vehicles -- two tanks and a jet. One of the tanks is in the picture (the one which forms the leg armor), but the jet formed the helmet and the other tank the drill missiles. So unless they are not showing us all of the parts, it looks like one of the tanks is fully transformable, but the other two components are not.

The components also combined together to make a robot on their own, if I remember right. It was definitely a "combiner Godbomber" to mix metaphors.

I'm thinking that that one head is an actual head for the "dummy" body, since it is smaller than the other head, which serves as more of a helmet that goes over your actual Gridman (not dummy) figure.

No, youre right. It was a Drill Tank, some kind of double barrel tank, and a jet.