I really don't think of the Caliber as filling that void at all. It isn't sporty, and it's too big to be considered in the class of the Nomad. The Nomad/Curve are built on the Sky/Solstice platform. They're tiny two seaters.. miata sized. The Caliber can fit 5 + luggage.
The Caliber is competing with the likes of the Mazda 3, Ford Focus and Impreza wagon.. It's the same thing as the PT Cruiser is now.... a Neon based 5 door. I don't understand the big deal about the Caliber on this forum or how it got included.