Offroad poptop caravans (or similar)

Looking to head around Australia with the wife and 2 kids (2 and 4). Will be taking a dual-cab 4WD with full camping setup on the tray, but also looking to tow something bigger and more comfortable, but still able to negotiate offroad conditions. Basic plan is caravan camper for a base-station, and use the 4WD camper for rugged expeditions.

I've looked at the Jayco Outback, Coromal campers and Goldstream campers. They all looked ideal in regards to layout - good floorplan, and nice and low when towing (or the ability to put a tinny on top).

I have concerns about their offroad ability. The warranties for these don't give much confidence, given some brands aren't covered on roads only traversable by 4WD vehicles.

Maximum budget is under $30,000. I'd rather stay away from soft-floor trailers, or anything that isn't able to be set up and packed up quickly when only stopping overnight.

So anyone know of options I should check out, that basically have similar floorplans to the above-mentioned, and can handle true offroad conditions?

Thanks in advance,
Ranga