If only you guys had Holden Commodore wagons or utes over there
The base model VY wagon (2003 onwards) with auto and 3.8L V6 gets 33mpg EPA and can easily fit a standard single mattress in the back with plenty of room for other goodies, the newer models and manual versions are even better for fuel economy
if you wanted even more storage space the ute with a panel van style canopy would be perfect, you could add a kamm back or a boat tail to get back the losses you have with a higher roof
They have great towing ability and with the upgraded county pack suspension they are alright off road too, if you want to go further off road they have an all wheel drive version called the Adventra
I have an earlier 1998 model with the same body shape but older interior and front/rear styling and its an awesome all rounder, soaks up highway miles with ease, is fun enough in the twisties and tows great, plus all the creature comforts of a modern sedan