Alanpeng, I can't add anything to the design comments... It's all been said by other contributors.
However, I would underline the comments about quality and robustness.
Chinese products have a poor reputation in Australia, being seen as built poorly to keep the price low. Whether this is right or wrong, it is just the way it is. Taiwan, Korea, and Japan all faced the same problem when they first started to export to Australia.
Part of the problem is that Australian conditions are very harsh, and products that don't take that into account don't survive here, damaging the manufacturer's reputation in the process.
As an example, Toyota and Nissan overcame the problem by building a 4WD that could survive the Australian conditions, Kia and Great Wall still have to learn this lesson.
Cheap campers are plentiful in Australia, but they do not fare well. If you are going to do this, you need to build something that can survive more than a couple of trips before becoming a wreck.
If you are serious, you'll need to trial your prototype. I've trialled vehicles in the past, and it isn't simply a matter of going out for the weekend. Your prototype is going to have to spend at least a month on all types of roads.... Australian roads.... before you know what will break.
I'm not saying you should bush-bash the prototype, but you need to take it the places your target market is likely to take it.... And it needs to come out the other side without major faults.
Another thing.... Australians hate being lied to. If you are going to market as an off-road unit, then make sure it is capable of weeks of corrugated dirt highways and the occasional river crossing. If not, then market as an on-road unit.
If you really want to trial your prototype, let me know. I normally rent a camper for my annual family holiday, and I normally write a performance report for the manufacturer as a courtesy. Perhaps we can arrange for your prototype to spend four weeks doing what Australians will expect it to be able to do.
Good luck with your business venture.
Cheers, Bob