I don't think you could drop it into the lower part of the hatch. There's too much stuff in there and I don't think there'd be room - hatch opening handle, lock, etc. I'm thinking these would get in the way.

A pop out or even a removable one, like the moonroof window would be cool though.

The reason I don't think this has been done and why Nissan didn't offer it is because of the issue with exhaust fumes. They tend to "puddle" behind the truck while it was going down the road. If you had an open window there, the fumes would then come into the truck. Just a thought...

-G