If there is no convenient way to do it legally, perhaps with some sort of temporary permits etc, ask the seller if they'd mind the Camper be kept in their name for the time being for you to have the 6 week holiday and then give them notice when it is all done and dusted at your end with the change over when back home.
If there is a rego transfer document signed on the day of the sale, they the seller is protected should something bad happen when you are traveling.
Insurance, you can get the insurance cover on the day of purchase, just tell them it will take an unknown time to get home. As long as you tell them, it is OK.
I have done something similar to this with a car, not planned, but events changed on my way home to Cairns from Syd where I got it, I just called the seller and told them, and the insurance and told them as well, as long as I tell them, all was well.
Have fun
Dave