If someone tried a dual axle, then this would have made the car wider, because between the two wheels is no room for another pair of wheels. So there could be a fun version for sure, but it will probably not have the same body as the original car.
Also there are tons of camper vans based on the T3. I had one myself from 1992 to 1997. It had mighty 57 horsepowers and worked very hard on climbing out of the Werratal on motorway A7 going south. On the motorway I could only overtake other T3 with the 50 hp Diesel engine. But the car was a masterpiece of engineering when you look at how they used the room they had inside. And, among most of the mini vans in that time, your legs were relatiely safe in case of a crash, because there were iron bars to keep the surviving space in the front.