Wheel size on a van won't worry the hub or brakes, only 2 sizes and they relate to actual weight of the rig and interestingly the difference between 10" and 12" brakes is diameter the shoes have the same area I was amazed to discover.
Heres a link to a page I did on slinging the axle under the springs
https://www.expandasdownunder.com/threads/underslinging-a-straight-axle.10987/
kept simple but it only applies to single beam axle set up, off set and duals are another thing again.
Before you do anything you must do some measuring of the tow bar height, (full tank of fuel) on flat ground measure the tow bar height as well as its height on different settings if you have an adjustable shank, measure the draw bar hitch height when level, it should ideally be about 25mm lower than the tug's, add the proposed increase in height to your van figure add 25mm to it and that should give you a rough position of where your tug tow ball would be, this way you can see if its a good proposition or not without the hard yacka, you may need to get a new shank for your tow bar.....
Is the lift for practical reasons like the vans bum drags on driveways or cosmetic ??? As I said before you can go from 10mm to about 80mm let us know how much you want and what the tyre size you have at the moment,.