Help with deciding tow vehicle

[The Monty]

Hey guys.
My Grandparents are after suggestions for a tow vehicle for their caravan.
Here is the core things they need:
Comfort
Ability to tow 2000kg plus
Must be 4wd to go onto the beach and into rough terrain
Must be ok on fuel
high teens, low $20k at auction prices (only buy from auctions)
Im open to suggestions, what do people here think?
I said Territory, 6 speed auto, AWD.
I say this as the gearbox is world class, its a basic falcon engine and gearbox so parts arent a problem, and there are plenty of ones around for parts. Its easy to convert to gas, to save on running costs, its got plenty of torque from low down, and they are fairly comfy.
The only negatives are the rust problems (how much warranty on rust do you get these days, 5 years still?), and its a bit thirsty when towing, as is everything when towing.
If we get one for the right price, it will get an LPG conversion, probably a custom tune to help with economy, and a proper tow kit and built auto to suit towing with large trans, it needs to last around ten years, as thats about as long as they want to keep driving.
Anyone else got any suggestions for me please?
Thanks.
Josh